WeKnowSmartHome

Smart home glossary

Every term you'll meet in a smart home, from 433 MHz to Z-Wave and everything in between — 138 definitions in plain language. Jump to a letter, or read straight through.

# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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2.4 GHz: The radio band shared by Wi-Fi, Zigbee, Thread, and Bluetooth. Crowded, but it travels through walls better than 5 GHz. Congestion here is a common cause of unreliable smart home devices.
Read more Getting signal into the garden, shed and garage FAQ: Why do so many smart devices need 2.4 GHz Wi-Fi?
5 GHz: The faster, shorter-range Wi-Fi band. Most smart home devices do not support it and need a 2.4 GHz network available — a frequent setup failure on combined-band routers.
Read more FAQ: Why does my device refuse to join my Wi-Fi?
433 MHz: A sub-GHz radio band used by older and budget European smart home devices — plugs, blinds, doorbells, and remotes, including KlikAanKlikUit. Usually one-way and unencrypted, with no mesh and no delivery confirmation. Cheap and simple, but a poor foundation for security-sensitive devices. See our 433 MHz explainer.
Read more Smart home protocols FAQ: What is 433 MHz, and should I still use it?
868 MHz: The sub-GHz band used by Z-Wave in Europe, and by some proprietary systems such as Homematic IP. Less congested than 2.4 GHz and better at penetrating walls.
Read more Smart home protocols FAQ: What are sub-GHz bands, and why do they matter?
915 MHz: The sub-GHz band used by Z-Wave in North America. A US Z-Wave device will not work on an EU network and vice versa, because the radios are region-locked to different frequencies.
Read more Smart home protocols FAQ: Why can't I use a US Z-Wave device in Europe?
802.11: The IEEE standard family behind Wi-Fi. Version letters indicate the generation — 802.11n, 802.11ac (Wi-Fi 5), 802.11ax (Wi-Fi 6).
Read more Smart home protocols FAQ: Is Wi-Fi a good protocol for smart home devices?
802.15.4: The IEEE low-power radio standard that both Zigbee and Thread are built on. It defines the physical radio; Zigbee and Thread define what the messages mean.
Read more Smart home protocols FAQ: Are Zigbee and Thread the same thing?

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Action: The "then" part of an automation — what actually happens once a trigger fires and any conditions pass. Turning on a light, sending a notification, closing a valve.
Read more Smart home automations FAQ: What is an automation?
Actuator: Any device that does something physical rather than measuring it: a relay, a motor, a valve, a lock. The counterpart to a sensor.
Read more FAQ: What is the difference between a sensor and an actuator?
Advanced Flow: Homey's visual automation editor for multi-step logic with branching, parallel paths, and multiple conditions on one canvas — as opposed to a simple linear if-this-then-that rule.
Read more Smart home automations
AES-128: The encryption standard used to secure Zigbee, Z-Wave, and Thread traffic. Its presence is why a modern mesh device is far harder to spoof than a legacy 433 MHz one.
Read more Securing the smart home itself FAQ: Is smart home radio traffic encrypted?
Alexa: Amazon's voice assistant and smart home ecosystem, built around Echo hardware. Has the largest third-party device and skill catalogue of any ecosystem, and is cloud-dependent by design.
Read more Amazon Alexa profile FAQ: Do I need Alexa, Google Home or Apple Home as well as a dedicated hub?
Ambient light sensor: A sensor (often built into motion sensors) reporting how bright a room is, measured in lux. Lets an automation skip turning lights on in daylight.
Read more Motion lighting that nobody resents
Apple Home: Apple's smart home ecosystem, built on the HomeKit framework. Automations run locally on an Apple TV, HomePod, or iPad acting as a home hub, with privacy as an explicit design goal.
Read more Apple Home profile FAQ: Which ecosystems support Matter?
App (hub app): On platforms like Homey, an "app" is a driver package that teaches the hub to speak to a particular brand's devices. Different from a phone app — closer to what Home Assistant calls an integration.
Read more Smart home hubs FAQ: What are integrations, apps and add-ons?
Association (Z-Wave): A direct device-to-device link in Z-Wave, letting a switch control a light without the hub relaying the command. Faster, and it keeps working if the hub is offline.
Read more Smart home protocols FAQ: How does Z-Wave work?
Automation: A saved rule that runs without you: a trigger, optional conditions, and one or more actions. Called a Flow on Homey, a Routine on Alexa and Google, an Automation on Home Assistant and Apple Home.
Read more Smart home automations FAQ: What is an automation?

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Backup and restore: Saving your hub's device pairings and automations so they can be recovered. Critical before firmware updates, and the difference between a five-minute and a five-hour recovery after a hub failure.
Read more FAQ: Should I back up my hub?
Binding (Zigbee): Zigbee's equivalent of Z-Wave association — a direct link between two devices that bypasses the hub for lower latency.
Read more Smart home protocols FAQ: How does Zigbee work?
Bluetooth Low Energy (BLE): A short-range, low-power version of Bluetooth used by locks, sensors, and wearables. Range is roughly 10–30 m. Without a bridge, BLE devices generally can't be controlled from outside the home.
Read more Smart home protocols FAQ: What is Bluetooth Low Energy used for?
Border router: A device that bridges a Thread mesh onto your regular Wi-Fi or Ethernet network. Increasingly built into speakers, displays, and TV boxes rather than bought separately. Thread devices need at least one.
Read more Thread border routers FAQ: What is a Thread border router, and do I already own one?
Bridge: Hardware or software that translates between two protocols or ecosystems — for example exposing Zigbee devices to Matter, or putting Hue bulbs on your network. See also gateway.
Read more Matter bridges FAQ: What is the difference between a hub, a bridge and a gateway?
Bulb base: The fitting type of a light bulb: E27 and E14 screw fittings (common in Europe), B22 bayonet (UK), GU10 and MR16 spotlights, E26 (North America). Getting this wrong is the most common smart bulb buying mistake.
Read more Best Buys: Smart Bulbs FAQ: Why won't my smart bulb fit?

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C-wire (common wire): A wire supplying continuous power to a thermostat. Many older homes lack one, which is the single most common smart thermostat installation blocker. Some thermostats ship a power-extender kit to work around it.
Read more Best Buys: Smart Thermostats FAQ: What is a C-wire, and why does my thermostat need one?
CCT (correlated colour temperature): How warm or cool white light appears, measured in Kelvin. Roughly 2700 K is warm yellow, 4000 K neutral, 6500 K cold daylight. "Tunable white" bulbs let you vary it.
Read more Why your LEDs look wrong FAQ: What do lumens and Kelvin mean on a bulb?
Certification: Formal testing that a device meets a standard — Matter certification, Zigbee 3.0, Z-Wave Plus, or safety marks like EN 14604 for smoke alarms. Uncertified "compatible" devices may work but aren't guaranteed to.
Read more Best Buys: Smoke & CO Detectors FAQ: Does a "compatible with" label guarantee it will work?
Cloud-dependent: A device or platform that routes commands through a manufacturer's servers, so it stops working during an internet or service outage. The opposite of local control.
Read more When the internet drops FAQ: What does cloud-dependent mean?
CO detector: A carbon monoxide alarm. Distinct from a smoke detector — CO is odourless and needs its own sensor. Many units combine both.
Read more Smoke and CO alarms FAQ: Is a smart smoke alarm still a proper smoke alarm?
Condition: An optional test between a trigger and an action: "only if it's dark", "only if nobody's home". Conditions are what separate a useful automation from an annoying one.
Read more Smart home automations FAQ: Why add conditions to an automation?
Coordinator (Zigbee): The single device that forms and manages a Zigbee network, normally built into your hub. There is exactly one per network. See also router and end device.
Read more Smart home protocols FAQ: What are a Zigbee coordinator, router and end device?
CRI (colour rendering index): How accurately a light source renders colour, scored out of 100. Above 90 is good; cheap smart bulbs often sit in the 80s, which makes skin tones and food look slightly off.
Read more Why your LEDs look wrong FAQ: What is CRI on a light bulb?
CT clamp: A current transformer that clips around a live cable to measure power draw without breaking the circuit. Used by whole-home energy monitors where no P1 port is available.
Read more Choosing energy monitoring FAQ: What is a CT clamp?

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Dashboard: A custom screen showing the devices and readings you care about, often wall-mounted on a tablet. Home Assistant calls these Lovelace dashboards; Homey, Apple Home, and others have their own versions.
Read more Smart home hubs
Dead zone: An area where a device can't reliably reach the mesh. Usually fixed by adding a mains-powered device (which acts as a repeater) between the hub and the dead zone, not by moving the hub.
Read more Getting signal into the garden, shed and garage FAQ: Is it better to move the hub or add a repeater?
Deadbolt: The solid bolt that actually secures a door. A smart lock's physical security comes from the deadbolt body and strike plate, not its software — which is why full-grade deadbolts matter more than feature lists.
Read more Best Buys: Smart Locks FAQ: How secure is a smart lock?
Dimmer: A switch that varies brightness rather than just switching. Note that not all bulbs are dimmable, and pairing a dimmer with a non-dimmable LED causes flicker and buzzing.
Read more Dimming without the flicker and buzz FAQ: Why does my LED flicker or buzz on a dimmer?
DIN rail module: A relay, dimmer, or meter that mounts inside the consumer unit or fuse box rather than behind a wall switch. Preferred for new builds because everything lives in one place and can switch whole circuits.
Read more Best Buys: Switches & Dimmers
Direct association: See association.
Read more Smart home protocols FAQ: How does Z-Wave work?
Dual-band: A router broadcasting both 2.4 GHz and 5 GHz. Some smart devices fail to pair if both bands share one network name — temporarily splitting them is a standard fix.
Read more FAQ: Why does my device refuse to join my Wi-Fi?

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eCO2 (equivalent CO2): An estimate of CO2 derived from VOC readings, not a real measurement. Cheaper air quality monitors report eCO2; a true NDIR sensor measures actual CO2 and is what you want for ventilation automation.
Read more Best Buys: Air Quality Monitors FAQ: What is the difference between eCO2 and real CO2?
Edge computing: Processing data on the device or hub rather than in the cloud. Faster, more private, and it keeps working offline.
Read more When the internet drops FAQ: What is edge computing?
End device (Zigbee): A battery-powered Zigbee device that sleeps between reports and does not relay other devices' traffic. Sensors and buttons are end devices; they don't extend your mesh.
Read more Smart home protocols FAQ: What are a Zigbee coordinator, router and end device?
End of life (EOL): The point at which a manufacturer stops supporting a product. For cloud-dependent devices EOL can mean the device stops working entirely — a risk that local-control devices largely avoid.
Read more When the internet drops FAQ: What happens when a manufacturer stops supporting a device?
Energy monitoring: Measuring electricity consumption, either per-device (a smart plug) or whole-home (a P1 reader or CT clamps). The prerequisite for any serious energy-saving effort.
Read more Choosing energy monitoring FAQ: Why measure energy use at all?
EnOcean: An energy-harvesting protocol whose switches and sensors need no batteries, powered by the press of the button or ambient light. Common in commercial buildings, rarer in homes.
Read more Smart home protocols
Ethernet: Wired networking. The most reliable connection for a hub or border router, because it removes Wi-Fi congestion from the one device everything else depends on.
Read more Smart home hubs FAQ: What does my home network need for Matter?
Exclusion (Z-Wave): The process of removing a device from a Z-Wave network. A device must be excluded before it can be added to a different hub — skipping this is why "the lock won't pair" so often.
Read more Troubleshooting FAQ: Why won't my device pair?

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Fabric (Matter): One ecosystem's secure network of Matter devices. A device can belong to several fabrics at once — that's what multi-admin means in practice.
Read more Smart home protocols FAQ: How do I use one Matter device in two apps?
Firmware: The software running on a device itself. Updates fix bugs and add features, but can also change behaviour or privacy posture, which is why longevity tracking matters.
Read more Securing the smart home itself FAQ: Are firmware updates safe?
Flow: Homey's name for an automation. A simple Flow is one trigger, conditions, and actions; Advanced Flow adds branching and parallel logic.
Read more Smart home automations FAQ: What is an automation?
Frequency band: The slice of radio spectrum a protocol uses — see 2.4 GHz, 433 MHz, 868 MHz, 915 MHz. Bands are regulated per region, which is why some devices are region-locked.
Read more Protocols compared FAQ: What are sub-GHz bands, and why do they matter?

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Gateway: Broadly interchangeable with hub or bridge: a device connecting one protocol to your network. Brands use the words inconsistently.
Read more Matter bridges FAQ: What is the difference between a hub, a bridge and a gateway?
Geofencing: Using your phone's location to trigger automations when you enter or leave an area. Two radii work better than one: a wide zone to pre-heat as you approach, a tight zone for arrival itself.
Read more Presence detection FAQ: How do I use geofencing well?
Google Home: Google's smart home ecosystem and app, backed by Nest hardware. Strong voice recognition; cloud-dependent for automation logic.
Read more Google Home profile FAQ: Do I need Alexa, Google Home or Apple Home as well as a dedicated hub?
Group (Zigbee): A set of devices addressed by a single command so they respond simultaneously. Grouping bulbs prevents the visible "popcorn effect" where lights switch one after another.
Read more Ten smart lighting mistakes, and how to avoid them

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Home Assistant: The largest open-source home automation platform by integration count. Free, fully local, no mandatory account — and the steepest learning curve of any mainstream option. See our Hubs section.
Read more Home Assistant profile FAQ: What is Home Assistant?
HomeKit: Apple's smart home framework, now largely superseded in branding by Apple Home. Devices once needed HomeKit-specific certification; Matter has mostly removed that requirement.
Read more Apple Home profile FAQ: Which ecosystems support Matter?
Hub: The controller at the centre of a smart home: it speaks one or more protocols, holds your device pairings, and runs your automations. See all 29 hubs we profile.
Read more Smart home hubs FAQ: What is a smart home hub?
Hysteresis: A deliberate gap between the switch-on and switch-off thresholds of an automation. Without it, a fan or heater rapidly cycles around a single setpoint. Essential for CO2, humidity, and temperature rules.
Read more Heating controls that actually save money FAQ: What is hysteresis and why does it stop a fan from cycling?

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IFTTT: "If This Then That" — a third-party cloud service linking apps and devices that don't natively talk. Convenient, but adds a cloud dependency and latency to anything routed through it.
Read more Smart home automations FAQ: What is IFTTT?
Infrared (IR): One-way, line-of-sight control used by most TV and air-conditioner remotes. An IR blaster lets a hub operate legacy AV gear, but it can't confirm the device actually responded.
Read more Smart home protocols FAQ: What is infrared control good for?
Integration: Home Assistant's term for a driver connecting a brand or service to the platform. Equivalent to an app on Homey.
Read more Smart home hubs FAQ: What are integrations, apps and add-ons?
Interoperability: Whether devices from different brands genuinely work together. The problem Matter was created to solve — see our interoperability matrix.
Read more Compatibility checker FAQ: What is interoperability, and why do people talk about it so much?
IP rating: Ingress protection, written as two digits: dust resistance then water resistance. IP44 handles splashes, IP65 handles jets, IP67 handles submersion. Check this before putting anything outdoors.
Read more Where to put an outdoor camera, and how to keep it weatherproof FAQ: What does an IP rating mean?
IPv6: The addressing scheme Thread is built on, giving every device its own address. Part of why Thread integrates with normal networking more naturally than Zigbee does.
Read more Matter over Thread FAQ: What does my home network need for Matter?

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Jamming: Deliberately flooding a radio band to stop devices communicating. A theoretical attack on wireless alarms; mitigated by systems that alert on unexpected radio silence.
Read more Alarm systems FAQ: Can wireless alarms be jammed?
Jeedom: A French open-source home automation controller with a plugin marketplace, popular in Francophone markets.
Read more Smart home hubs
Joining: See pairing. Zigbee documentation often says "joining" where Z-Wave says "inclusion".
Read more Troubleshooting FAQ: Why won't my device pair?

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Kelvin (K): The unit for colour temperature. Confusingly, lower numbers look warmer: 2700 K is cosy yellow, 6500 K is cold blue-white.
Read more Why your LEDs look wrong FAQ: What do lumens and Kelvin mean on a bulb?
Keypad: A numeric entry pad for arming an alarm or unlocking a door by code. Look for anti-peep designs that pad your real code with random digits.
Read more Keys, codes and credentials
KNX: An open, wired building-automation standard maintained by the KNX Association in Belgium. Dominant in European commercial and high-end residential work; needs structured wiring and a certified installer.
Read more Smart home protocols

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LAN (local area network): Your home network. Local discovery over the LAN (via mDNS or SSDP) is what lets a hub find and control devices without any cloud round-trip.
Read more Securing the smart home itself FAQ: Should I put smart devices on their own network?
Latency: The delay between trigger and action. Local processing is typically tens of milliseconds; a cloud round-trip can be a second or more, which is very noticeable on a light switch.
Read more FAQ: Why is there a delay between pressing a button and the light?
Local control: Commands and automations handled on your own network with no cloud dependency. The single most important attribute for reliability, because it survives internet outages and vendor shutdowns.
Read more When the internet drops FAQ: What does local control mean, and why does it matter?
Lumen (lm): How much light a bulb emits. The number that actually matters when replacing an old bulb — roughly 800 lm equals a traditional 60 W incandescent.
Read more Best Buys: Smart Bulbs FAQ: What do lumens and Kelvin mean on a bulb?
Lux: Light falling on a surface, as reported by an ambient light sensor. Used in automations like "only switch on below 50 lux".
Read more Lighting a room properly

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Mains-powered: Permanently wired or plugged in. On Zigbee and Z-Wave, mains-powered devices normally act as repeaters, so scattering a few of them is how you strengthen a mesh.
Read more Smart home protocols FAQ: Which protocol is best for battery-powered sensors?
Matter: An application-layer standard from the Connectivity Standards Alliance that lets certified devices work across Alexa, Google Home, Apple Home, and SmartThings with one certification. It runs over Wi-Fi, Thread, or Ethernet — it is not a radio protocol. See our Matter explainer.
Read more Smart home protocols FAQ: What is Matter?
mDNS: Multicast DNS, the mechanism letting devices announce themselves on the local network so a hub can find them without cloud lookup.
Read more Matter over Wi-Fi FAQ: What does my home network need for Matter?
Mesh network: A network where devices relay each other's traffic, so coverage grows as you add mains-powered devices. Zigbee, Z-Wave, and Thread are meshes; Wi-Fi is not.
Read more Smart home protocols FAQ: What is a mesh network?
Migration: Moving your devices and automations from one hub to another. Zigbee and Z-Wave devices must be individually unpaired and re-paired; Matter devices are far easier thanks to multi-admin.
Read more Switching hubs FAQ: How hard is it to switch to a different hub?
mmWave: Millimetre-wave radar that detects a person who is present but perfectly still. Solves the classic "lights turn off while I'm sitting here" failure of PIR sensors. Higher power draw, so usually mains-powered.
Read more Best Buys: Motion & Presence Sensors FAQ: What is the difference between a motion sensor and a presence sensor?
Multi-admin: A Matter feature letting one device be controlled by several ecosystems simultaneously — the same plug live in both Alexa and Apple Home. Generate a sharing code in the first app, scan it in the second.
Read more Smart home protocols FAQ: How do I use one Matter device in two apps?
Multi-protocol: A hub speaking several radio protocols natively. Homey Pro is the broadest example with seven; most hubs manage two to four.
Read more Compatibility checker FAQ: What is a multi-protocol hub?

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NDIR sensor: Non-dispersive infrared — the sensor type that genuinely measures CO2, as opposed to estimating it (eCO2). Worth paying for if you plan CO2-triggered ventilation.
Read more Best Buys: Air Quality Monitors FAQ: What is the difference between eCO2 and real CO2?
Node: Any individual device on a mesh network. Z-Wave networks have a documented node limit (232 classic), which matters in very large installations.
Read more Smart home protocols FAQ: What is a mesh network?
NVR (network video recorder): A box that records camera footage locally. The alternative to a cloud video subscription, and the reason PoE cameras appeal to people avoiding monthly fees.
Read more Best Buys: Smart Cameras FAQ: How do I record camera footage without a cloud subscription?

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OCPP: Open Charge Point Protocol, the open standard for EV chargers. Support for it means a charger isn't locked to one vendor's app or backend.
Read more Best Buys: EV Chargers FAQ: What should I look for in a smart EV charger?
Occupancy sensor: A sensor reporting whether a space is in use. Usually PIR or mmWave; the two fail in different ways, which is why combining them cuts false triggers.
Read more Measuring how an office is actually used, without monitoring people FAQ: What is the difference between a motion sensor and a presence sensor?
ONVIF: An open standard for IP cameras. ONVIF or RTSP support means any hub or NVR can record the stream without the manufacturer's cloud.
Read more Best Buys: Smart Cameras FAQ: How do I record camera footage without a cloud subscription?
OpenTherm: A communication standard between a thermostat and a modulating boiler, allowing the boiler to run at partial output rather than simply on/off. More efficient and more comfortable, common in European heating.
Read more Best Buys: Smart Thermostats FAQ: What is OpenTherm?
OTA update: Over-the-air firmware update, delivered wirelessly. Convenient, but it also means a device's behaviour can change after you've bought it.
Read more Securing the smart home itself FAQ: Are firmware updates safe?

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P1 port: A standardised data port on smart electricity meters in the Netherlands and much of Europe. A P1 reader gives exact whole-home consumption straight from the meter — more accurate than CT clamps.
Read more Getting your own data out of a smart meter FAQ: What is a P1 port?
Pairing: Adding a device to a hub or network. Called inclusion on Z-Wave, joining on Zigbee, commissioning on Matter. Most pairing failures come from a device still being paired to a previous hub.
Read more Troubleshooting FAQ: Why won't my device pair?
PIR sensor: Passive infrared — detects movement by changes in heat. Cheap, battery-friendly, and the standard motion sensor. Its weakness is that a motionless person becomes invisible to it.
Read more Motion lighting that nobody resents FAQ: What is the difference between a motion sensor and a presence sensor?
PM2.5: Airborne particles under 2.5 micrometres, the fraction most associated with health effects. The key reading on an air quality monitor alongside CO2.
Read more Indoor air quality FAQ: What are PM2.5 and VOC readings?
PoE (Power over Ethernet): Power and data over one Ethernet cable. The preferred way to install cameras: no batteries, no Wi-Fi congestion, no separate power supply.
Read more Where to put an outdoor camera, and how to keep it weatherproof
Presence detection: Determining whether people are home, via phone geofencing, Bluetooth or Wi-Fi presence, or mmWave. The most useful and most unreliable input in home automation.
Read more Presence detection FAQ: Why is presence detection so unreliable?
Protocol: The language devices use to communicate. See our Protocols section for all ten covered here.
Read more Smart home protocols FAQ: What is a smart home protocol?

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QR setup code (Matter): The code printed on a Matter device (or shown in its app) used to commission it. Keep it — you may need it again, and a device sharing code for multi-admin is generated separately.
Read more Matter over Thread FAQ: Should I keep the Matter QR code?
Quiet hours: A time window in which an automation is suppressed or notifications are silenced. The simplest fix for automations that are useful by day and infuriating at 3 a.m.
Read more Night-time safety FAQ: What are quiet hours?

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Relay: An electrically operated switch. Smart relays and switch modules sit behind existing switches or inside fittings so your original faceplates keep working.
Read more Best Buys: Switches & Dimmers FAQ: What is the difference between a smart plug, a switch module and a smart bulb?
Repeater: Any mains-powered mesh device that relays traffic and extends coverage. Adding a plug or bulb between hub and problem area is usually more effective than moving the hub.
Read more Getting signal into the garden, shed and garage FAQ: Is it better to move the hub or add a repeater?
RGBW / RGBWW / RGBCCT: Colour bulb configurations. RGBW adds a dedicated white LED to red-green-blue; RGBCCT adds tunable warm and cool white. Dedicated white channels produce far better whites than mixing RGB.
Read more Best Buys: LED Light Strips FAQ: What do RGBW, RGBWW and RGBCCT mean?
Router (Zigbee): A mains-powered Zigbee device that relays traffic for others. Not to be confused with your internet router. See also coordinator and end device.
Read more Smart home protocols FAQ: What are a Zigbee coordinator, router and end device?
RTSP: Real Time Streaming Protocol, the standard way to pull a camera's video stream locally. Its presence (or absence) determines whether you can record without the vendor's cloud.
Read more Best Buys: Smart Cameras FAQ: How do I record camera footage without a cloud subscription?

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Scene: A saved set of device states recalled together — "Movie night" dimming lights and closing blinds. Unlike an automation, a scene doesn't decide when to run; something else triggers it.
Read more Smart home automations FAQ: What is the difference between a scene and an automation?
Sensor: A device that measures rather than acts: motion, contact, temperature, humidity, leak, air quality. The input layer of every automation.
Read more Devices FAQ: What is the difference between a sensor and an actuator?
SmartThings: Samsung's smart home ecosystem, originally an independent US startup acquired in 2014. Wide protocol support with a hybrid cloud/local model.
Read more Samsung SmartThings overview profile FAQ: Which ecosystems support Matter?
SSDP: Simple Service Discovery Protocol, another local-network discovery mechanism alongside mDNS.
Read more FAQ: Should I put smart devices on their own network?
Sub-GHz: Radio bands below 1 GHz — 433, 868, and 915 MHz. Better wall penetration and less congestion than 2.4 GHz, at lower data rates.
Read more Protocols compared FAQ: What are sub-GHz bands, and why do they matter?
Switch module: A small relay fitted behind an existing wall switch or inside a ceiling rose, adding smart control while keeping your existing faceplate and manual operation.
Read more Best Buys: Switches & Dimmers FAQ: What is the difference between a smart plug, a switch module and a smart bulb?

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Thread: A low-power, IPv6-based mesh protocol built on 802.15.4, designed as the radio backbone for Matter. Needs a border router. See our Thread explainer.
Read more Matter over Thread FAQ: What is Thread?
Thread border router: See border router.
Read more Thread border routers FAQ: What is a Thread border router, and do I already own one?
Trigger: The event that starts an automation: motion detected, door opened, sunset, a time, a button press, a threshold crossed.
Read more Smart home automations FAQ: What is an automation?
TRV (thermostatic radiator valve): A motorised valve replacing the manual knob on a radiator, giving per-room temperature control in homes with no heating zones. The cheapest route to room-by-room heating in older European housing.
Read more Best Buys: Smart Radiator Valves FAQ: What is a smart radiator valve?
Tunable white: A bulb whose colour temperature can be adjusted without full colour capability. Enough for circadian lighting, and usually better quality white than a colour bulb.
Read more Circadian lighting FAQ: What do lumens and Kelvin mean on a bulb?
Two-way communication: A device that confirms it received a command and reports its state back. One-way protocols like most 433 MHz and infrared can't, so the hub never truly knows the device's state.
Read more Smart home protocols

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UL certification: A North American safety certification. UL 217 covers smoke alarms; the European equivalent is EN 14604. Relevant to insurance and building regulations, not just quality.
Read more Best Buys: Smoke & CO Detectors FAQ: Is a smart smoke alarm still a proper smoke alarm?
Unpairing: Removing a device from a network so it can be added elsewhere. See exclusion. Skipping it is the most common cause of "this device won't pair".
Read more Troubleshooting FAQ: Why won't my device pair?
UPS (uninterruptible power supply): A battery backup keeping your hub and router alive through a power cut. Without one, "local control" still fails when the electricity does.
Read more When the internet drops FAQ: Why does everything stop in a power cut when my hub is local?

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VLAN: A logically separated network segment. Putting smart devices on their own VLAN limits what a compromised device can reach — the standard hardening step for a large smart home.
Read more Securing the smart home itself FAQ: Should I put smart devices on their own network?
VOC (volatile organic compounds): Airborne chemicals from paint, cleaning products, and furnishings, reported by air quality monitors. Also the basis for estimated eCO2 figures.
Read more Indoor air quality FAQ: What are PM2.5 and VOC readings?
Voice assistant: Alexa, Google Assistant, or Siri. Worth separating in your head from the hub: the assistant is an input method, the hub runs the logic. Most homes benefit from both.
Read more Smart home hubs FAQ: Is a voice assistant the same as a hub?

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Watt (W): A unit of power draw. On LED bulbs it no longer indicates brightness — use lumens for that. Relevant for checking a smart plug's load rating.
Read more Which appliances actually cost you money FAQ: How do I find out which appliance wastes the most?
Wi-Fi: Standard wireless networking. Simple for always-powered devices, poor for battery sensors because the radio draws far more power than a mesh protocol. See our Wi-Fi explainer.
Read more Smart home protocols FAQ: Is Wi-Fi a good protocol for smart home devices?
WPA3: The current Wi-Fi security standard. Some older smart devices can't join WPA3-only networks, which is why routers often run a mixed WPA2/WPA3 mode.
Read more Securing the smart home itself FAQ: Does WPA3 break smart devices?

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X10: One of the earliest home automation protocols, dating to the 1970s, sending signals over household electrical wiring. Almost entirely obsolete, but still occasionally found in older installations.
Read more Smart home protocols
Xiaomi / Mi Home: A large, very inexpensive ecosystem of Zigbee and Wi-Fi devices. Strong value, though it leans heavily on Xiaomi's cloud and has had region-locking friction in Europe.
Read more Xiaomi profile

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Y-plan / S-plan heating: Two common UK central heating layouts. Y-plan uses one three-port valve for heating and hot water; S-plan uses separate two-port valves. Which one you have determines what thermostat wiring you need.
Read more Zoning your heating without spending a fortune

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Zigbee: A mature low-power mesh protocol on 2.4 GHz, built on 802.15.4, with the largest device catalogue of any smart home radio. Needs a hub. See our Zigbee explainer.
Read more Smart home protocols FAQ: How does Zigbee work?
Zigbee 3.0: The unified Zigbee certification that replaced earlier fragmented profiles, greatly improving cross-brand compatibility.
Read more Smart home protocols FAQ: What is Zigbee 3.0?
Zigbee2MQTT: Open-source software bridging a Zigbee USB dongle to any MQTT-capable platform, bypassing vendor hubs entirely. Popular with Home Assistant users.
Read more Home Assistant profile FAQ: What are Zigbee2MQTT and Z-Wave JS?
Zone: A logical grouping — a room or floor in a hub, a heating circuit in an HVAC system, or an irrigation circuit on a sprinkler controller. Meaning depends on context.
Read more Zoning your heating without spending a fortune
Z-Wave: A mesh protocol on sub-GHz frequencies (868 MHz in the EU, 915 MHz in the US), with strict cross-brand certification from the Z-Wave Alliance. Region-locked by frequency. See our Z-Wave explainer.
Read more Smart home protocols FAQ: How does Z-Wave work?
Z-Wave JS: The modern open-source Z-Wave driver used by Home Assistant and others, which replaced the older OpenZWave project.
Read more Home Assistant profile FAQ: What are Zigbee2MQTT and Z-Wave JS?
Z-Wave Long Range (Z-Wave LR): A newer Z-Wave variant trading mesh networking for much greater point-to-point range, useful for outbuildings, gates, and large properties.
Read more Smart home protocols FAQ: What are Z-Wave Plus and Z-Wave Long Range?
Z-Wave Plus: A certification tier bringing better battery life, range, and OTA update support. Effectively the baseline to look for on any Z-Wave purchase today.
Read more Smart home protocols FAQ: What are Z-Wave Plus and Z-Wave Long Range?