The homeowner's parts glossary
Updated August 2026
Plain-English definitions for the parts your house actually runs on: what each one is, where to find it, what it does, and how often it needs attention. Every term links to a short reference you can read in two minutes, no trade background required.
Electrical
- 200 amp service
200-amp service is an electrical supply rated to…
- AFCI
An AFCI, or arc fault circuit interrupter, is…
- aluminum wiring
Aluminum wiring is solid aluminum branch-circuit wire, used…
- carbon monoxide detector
A carbon monoxide detector is an alarm that…
- ceiling fan
A ceiling fan is a motor and blade…
- circuit breaker
A circuit breaker is a resettable safety switch…
- doorbell transformer
A doorbell transformer is a small steel-cased device…
- double-pole breaker
A double-pole breaker is a breaker that fills…
- electrical panel
An electrical panel, also called a breaker box…
- EV charger
An EV charger, properly called electric vehicle supply…
- Federal Pacific panel
A Federal Pacific panel is an electrical panel…
- GFCI breaker
A GFCI breaker is a circuit breaker with…
- GFCI outlet
A GFCI outlet, short for ground fault circuit…
- home battery
A home battery is a wall- or floor-mounted…
- knob and tube wiring
Knob and tube wiring is the pre-1950s wiring…
- portable generator
A portable generator is a wheeled engine and…
- smoke detector
A smoke detector is a ceiling- or wall-mounted…
- solar inverter
A solar inverter is the electronics box that…
- solar panel
A solar panel is a sealed laminate of…
- subpanel
A subpanel is a second breaker box fed…
- transfer switch
A transfer switch is a switch that connects…
- whole-house generator
A whole-house generator, called a standby generator in…
- whole-house surge protector
A whole-house surge protector is a clamping device…
Hvac
- AFUE rating
AFUE, short for Annual Fuel Utilization Efficiency, is…
- air handler
An air handler is the indoor cabinet of…
- blower motor
A blower motor is the electric motor in…
- boiler
A boiler is a heater that warms water…
- BTU
A BTU, or British thermal unit, is the…
- central air conditioner
A central air conditioner is a two-piece split…
- condensate drain line
A condensate drain line is the small white…
- condensate pump
A condensate pump is a small plastic reservoir…
- condenser unit
A condenser unit is the outdoor half of…
- contactor
A contactor is an electrically operated switch inside…
- draft inducer
A draft inducer is the small fan that…
- evaporator coil
An evaporator coil is the indoor coil of…
- flame sensor
A flame sensor is a thin metal rod…
- furnace
A furnace is a forced-air heater that burns…
- furnace igniter
A furnace igniter is the element that glows…
- heat exchanger
A heat exchanger is the sealed steel chamber…
- heat pump
A heat pump is an electric system that…
- HRV
An HRV, or heat recovery ventilator, is a…
- HVAC capacitor
An HVAC capacitor is a small metal cylinder…
- HVAC filter
An HVAC filter is the disposable pleated panel…
- MERV rating
A MERV rating is a 1 to 16…
- mini-split
A mini-split is a ductless heat pump: a…
- pilot light
A pilot light is a small gas flame…
- radiator
A radiator is the metal unit in a…
- SEER rating
A SEER rating is the cooling an air…
- thermostat
A thermostat is the temperature sensor and low-voltage…
- ton of cooling
One ton of cooling is a rate of…
- whole-house dehumidifier
A whole-house dehumidifier is a dehumidifier that plumbs…
- whole-house humidifier
A whole-house humidifier is a unit strapped to…
Kitchen-appliances
- convection oven
A convection oven is an oven with a…
- dishwasher air gap
A dishwasher air gap is the small chrome…
- downdraft vent
A downdraft vent is kitchen ventilation that grabs…
- ice maker
An ice maker is the automatic machine that…
- induction cooktop
An induction cooktop is the built-in, oven-free version…
- induction range
An induction range is a freestanding stove that…
- range hood
A range hood is the powered canopy above…
- refrigerator compressor
A refrigerator compressor is the sealed pump at…
- refrigerator water filter
A refrigerator water filter is a replaceable activated-carbon…
Laundry
- dryer vent
A dryer vent is the duct that carries…
- dryer vent booster fan
A dryer vent booster fan mounts partway along…
- heat pump dryer
A heat pump dryer dries clothes the way…
- lint trap
Pull the mesh screen out of the dryer…
- washer supply hose
The two hoses screwed to the back of…
- washing machine drain pan
Washer drain pans are shallow trays, usually 1–2.5…
Outdoor-lawn
- hot tub
A hot tub, or spa, is an insulated…
- pool filter
A pool filter is the tank downstream of…
- pool heater
A pool heater is the appliance plumbed in…
- pool pump
A pool pump is the electric motor and…
- pressure washer
A pressure washer is a pump that takes…
- salt water chlorinator
A salt water chlorinator is a plumbed-in cell…
- sprinkler head
A sprinkler head is the pop-up nozzle at…
- sprinkler valve
A sprinkler valve is an electrically piloted water…
Plumbing
- angle stop
An angle stop is the small valve under…
- anode rod
An anode rod is a sacrificial metal rod…
- backflow preventer
A backflow preventer is a valve assembly that…
- battery backup sump pump
A battery backup sump pump is a second…
- brine tank
The brine tank is the squat tank standing…
- dip tube
The dip tube is a length of plastic…
- expansion tank
An expansion tank is a small steel tank,…
- faucet aerator
An aerator is the small screened insert threaded…
- faucet cartridge
A faucet cartridge is the removable valve body…
- flush valve
A flush valve is the large opening in…
- frost-free sillcock
A frost-free sillcock is an outdoor faucet built…
- garbage disposal
A garbage disposal is the motorized grinding chamber…
- heat pump water heater
A heat pump water heater is an electric…
- hose bib
A hose bib is the outdoor faucet mounted…
- main shutoff valve
The main shutoff valve is the one valve…
- P-trap
A P-trap is the U-shaped bend of pipe…
- plumbing vent
A plumbing vent is the dry pipe that…
- pressure reducing valve
A pressure reducing valve, or PRV, is a…
- pressure tank
A pressure tank is the steel tank on…
- septic drain field
The drain field, also called a leach field,…
- septic tank
A septic tank is a buried, watertight container,…
- sewage ejector pump
A sewage ejector pump is a pump in…
- sewer cleanout
A sewer cleanout is a capped access port…
- sewer line
A sewer line is the single buried pipe,…
- shower cartridge
A shower cartridge is the replaceable brass or…
- shower valve
A shower valve is the mixing valve buried…
- sump pump
A sump pump is an electric pump sitting…
- sump pump check valve
A sump pump check valve is a one-way…
- tankless water heater
A tankless water heater is a wall-mounted unit…
- toilet fill valve
The fill valve is the plastic tower standing…
- toilet flapper
A toilet flapper is the hinged rubber seal…
- TPR valve
A TPR valve is the temperature and pressure…
- water hammer arrestor
A water hammer arrestor is a small sealed…
- water heater
A water heater is the appliance that heats…
- water softener
A water softener is a tank of resin…
- wax ring
A wax ring is a molded doughnut of…
- well pump
A well pump is the electric pump that…
- whole-house water filtration system
Whole-house water filtration is a point-of-entry setup that…
Roofing-exterior
- asphalt shingle roof
An asphalt shingle roof is a roof covered…
- caulk bead
Caulk is a flexible sealant gunned from a…
- chimney cap
A chimney cap is the metal lid mounted…
- chimney crown
A chimney crown is the sloped slab of…
- chimney flue
The chimney flue is the passage inside a…
- crawl space
A crawl space is the shallow, unfinished gap…
- deck ledger board
A deck ledger board is the framing member…
- downspout
A downspout is the vertical pipe that empties…
- drip edge
A drip edge is the L-shaped metal strip…
- fascia board
Fascia is the long horizontal board that closes…
- fiber cement siding
Fiber cement siding is a siding board pressed…
- flashing
Flashing is thin sheet metal fitted at every…
- flat roof
A flat roof is a low-slope roof waterproofed…
- French drain
A French drain is a gravel-filled trench with…
- garage door opener
A garage door opener is the ceiling-mounted motor…
- garage door system
A garage door system is the door panels…
- garage door torsion spring
A garage door torsion spring is the tightly…
- gutter guard
A gutter guard is a cover fitted over…
- metal roof
A metal roof is a roof clad in…
- R-value
R-value is the number that measures how well…
- radiant barrier
A radiant barrier is a sheet of reflective…
- retaining wall
A retaining wall is a structure that holds…
- ridge vent
A ridge vent is a continuous exhaust vent…
- roof boot
A roof boot is the flanged collar that…
- skylight
A skylight is a window set into the…
- soffit
The soffit is the finished underside of a…
- soffit vent
A soffit vent is a perforated panel or…
- stucco finish
Stucco is a cement-based plaster applied wet in…
- vapor barrier
A vapor barrier is a sheet material, usually…
- vinyl siding
Vinyl siding is interlocking PVC panels that hang…
- weatherstripping
Weatherstripping is the flexible seal that runs around…
Safety-specialty
- egress window
An egress window is a window sized so…
- fire extinguisher
A fire extinguisher is a pressurized cylinder that…
- radon mitigation system
A radon mitigation system, in the sub-slab depressurization…
- smart water shutoff valve
A smart water shutoff valve is a motorized…
- water leak sensor
A water leak sensor is a battery-powered puck…
Seasonal-scenario
- ice dam
An ice dam is a ridge of solid…