The IES defines illumination engineering terms in ANSI/IES LS-1-20, which is available here online. You can search terms by their first letter using the categories listed in the Categories window, by the first letter of the term in the alphabetical list below, or by typing the term in the search window. You can find the Introduction material for LS-1-20 on these pages:
Copyright, Disclaimer, and American National Standards Statement
Foreword, Nomenclature Committee members, Introduction, and Scope
Spectral Parameters Used in Illumination Engineering
- a
- Abbe’s law
- absolute luminance threshold
- absolute photometry
- absorptance, α
- absorption
- accent lighting
- acceptance half-angle
- accommodation
- ace
- actinic
- action spectrum
- adaptation
- adaptive color shift
- adaptive lighting
- adaptive subdivision
- adverse weather lamp
- aerodrome beacon
- aeronautical beacon
- aeronautical ground light
- aeronautical light
- afterimage
- aging
- air mass (optical air mass)
- aircraft aeronautical light
- airway beacon
- Allard’s law
- altitude angle
- amalgam
- ambient lighting
- analog multiplex, AMX
- anchor light
- angle-of-approach lights
- angle of collimation
- Annex A - Physical Receptors and Devices
- annual operating hours
- annual sunlight exposure (ASE)
- anti-collision light
- aphakic hazard function
- apostilb
- approach-light beacon
- approach lights
- arc
- arc discharge
- arc lamp
- area lighting (television, film, theater)
- artificial pupil
- artificial sky
- artificial sky glow
- artificial sky "mirror box"
- asbestos tapoff
- astronomical time switch
- astronomical timeclock
- atmospheric transmissivity
- attenuation coefficient
- automated fixture
- auxiliary equipment
- average luminance
- aversion response
- azimuth
- b
- baby
- back light
- back-up lamp
- backing lighting
- backward ray tracing
- bactericidal functions
- bactericidal lamp
- bactericidal radiation
- baffle
- balcony lights
- ballast
- ballast factor
- ballast-lamp photometric factor
- bank
- bar (of lights)
- bare (exposed) lamp
- barn doors
- barrel
- barrette
- base light
- batten
- beacon
- beam angle
- beam axis of a projector
- beam efficiency
- beam lights
- beam lumens
- beam projector
- beam spread (in any plane)
- bed
- bi-level lighting control
- biconical reflectance
- biconical transmittance
- bidirectional reflectance
- bidirectional reflectance distribution function (BRDF)
- bidirectional scatter distribution function (BSDF)
- bidirectional transmittance
- bidirectional transmittance distribution function (BTDF)
- bihemispherical reflectance
- bihemispherical transmittance
- bilateral sidelighting
- bin
- binocular portion of the visual field
- biological rhythm
- black light
- black light flux
- black light flux density
- blackbody
- blackbody curve
- blackbody (Planckian) locus
- blacklight lamp
- blackout
- blending lighting
- blinding glare
- blinds
- Blondel-Rey law
- blue-light hazard
- blue-light hazard function
- board
- bollard
- boomerang (boom)
- borderlight
- borderline between comfort and discomfort (BCD)
- boundary lights
- bowl
- box boom
- bracket (mast arm)
- bridge (light bridge)
- brightness
- brightness contrast threshold
- brightness enhancement
- brightness (of a perceived aperture color)
- brightness ratio
- broad
- Broca-Sulzer effect
- brute
- bulb
- butterfly
- c
- camera light
- candela
- candlepower
- carbon arc
- carbon-arc lamp
- cavity ratio, CR
- ceiling area lighting
- ceiling cavity
- ceiling cavity ratio, CCR
- ceiling projector (search lighting)
- ceiling ratio
- center-beam candlepower (CBCP)
- center high-mounted stop lamp, CHMSL
- central (foveal) vision
- central visual field
- centroid wavelength
- channel
- channel lights (aeronautical lighting)
- characteristic curve
- chromatic adaptation
- chromatic color
- chromatic contrast threshold (color contrast threshold)
- chromaticity coordinates of a color, x,y,z
- chromaticity diagram
- chromaticity difference thresholds
- chromaticity of a color
- chromogenic glazing
- CIE 1988 2° modified spectral luminous efficiency function for photopic vision
- CIE (L*a*b*) uniform color space
- CIE (L*u*v*) uniform color space
- CIE photopic luminous efficiency function
- CIE scotopic luminous efficiency function
- CIE sky models
- CIE standard chromaticity diagram
- circadian
- circling guidance lights
- clear sky
- clearance lamps
- clerestory
- closed-loop control
- cloudy sky
- code (or character)
- coefficient of attenuation (at a point in a given direction), µ
- coefficient of beam utilization, CBU
- coefficient of utilization, CU
- coffer
- cold-cathode fluorescent lamp
- cold-cathode lamp
- color
- color comparison, or color grading
- color contrast thresholds
- color correction (of a photograph or printed picture)
- color difference thresholds
- color discrimination
- color frame
- color matching
- color matching functions (spectral tristimulus values)
- color media
- color preference index (of a light source)
- color rendering
- color rendering index (CRI) (of a light source)
- color space
- color temperature of a light source
- color tuning
- color wheel
- colorfulness of a perceived color
- colorimeter
- colorimetric purity of a light
- colorimetric shift
- colorimetry
- compact-arc lamp
- compact fluorescent lamp, CFL
- compact source iodide (CSI) lamp
- company switch
- comparison lamp
- complementary wavelength of a light
- complete diffusion
- concert border
- cones
- configuration factor, c1→2
- conical-directional reflectance
- conical-directional transmittance
- conical-hemispherical reflectance
- conical-hemispherical transmittance
- console
- conspicuity
- constant current transformer
- constant lumen output
- continuous daylight autonomy (cDA)
- continuous wave (CW) lamp
- contour light
- contrast
- contrast rendition factor, CRF
- contrast sensitivity
- contrast threshold
- control board
- cookie
- cornice lighting
- correlated color temperature (CCT) of a light source
- cosine-cubed law
- cosine law
- counter-key light
- country beam
- course light
- cove base
- cove lighting
- criteria rating
- critical task location
- cross connect
- cross fade
- cross fader
- cross-lighting
- cucoloris
- cue
- cut-off angle (of a luminaire)
- cutout
- cutter
- cyclorama (“cyc”)
- d
- dark adaptation
- daylight
- daylight autonomy (DA)
- daylight availability
- daylight coefficient
- daylight conversion filter
- daylight factor
- daylight harvesting
- daylight lamp
- daylight louver
- daylight management
- daylight window
- daylight zone
- daylighted
- daylighting
- daylighting system
- daylit
- densitometer
- designer’s remote
- deuce
- dichroic filter
- diffuse reflectance
- diffuse reflection
- diffuse sky radiation
- diffuse transmission
- diffuse transmittance
- diffused lighting
- diffusely reflective
- diffuser
- diffusing panel
- diffusing surfaces and media
- digital multiplex, DMX
- dim
- dimmer
- dimmer board
- dimmer curve
- dimmer per circuit
- dimming
- direct actinic effect (of optical radiation)
- direct component
- direct glare
- direct-indirect lighting
- direct lighting
- direct normal solar radiation
- direct photometry
- direct ratio
- direct solar radiation
- direct sunlight
- direct sunlight hours
- directional-conical reflectance
- directional-conical transmittance
- directional-hemispherical reflectance
- directional-hemispherical transmittance,
- directional lighting
- disability glare
- disability glare factor, DGF
- discomfort glare
- discomfort glare factor
- discomfort glare rating, DGR
- distal stimulus
- distribution temperature of a light source
- diurnal
- dominant wavelength of a light
- dose (optical radiation)
- dot
- double broad
- downlight
- downward component
- dowser
- driving beam
- driving light
- dual headlighting system
- dual-loop photosensor control
- dummy load
- dust-proof luminaire
- dust-tight luminaire
- Dutchman
- duty cycle
- dynamic glazing
- e
- E-viton (erytheme)
- effect projector
- effective ceiling cavity reflectance, ρcc
- effective floor cavity reflectance, ρfc
- effective intensity (search lighting)
- efficacy
- efficiency
- egress
- electric discharge
- electric-discharge lamp
- electrochromic glazing
- electrodeless fluorescent lamp
- electroluminescence
- electromagnetic spectrum
- elevation
- ellipsoidal reflector spotlight
- emergency exit
- emergency lighting
- emissivity
- emittance
- enclosed and gasketed luminaire
- equal interval (isophase) light
- equation of time
- equipment operating factor
- equivalent contrast, C̃
- equivalent contrast, C̃e
- equivalent luminous intensity of an extended source at a specified distance
- equivalent sphere illuminance, ESI
- equivalent veiling luminance
- erythema
- erythemal action spectrum
- erythemal dose
- erythemal effectiveness
- erythemal exposure
- erythemal flux
- erythemal flux density
- erythemal radiation
- erythemal threshold
- erythemal unit (EU)
- excitation purity of a light
- exempt group
- exit
- exit access
- exit discharge
- exit sign
- exitance
- exitance coefficient, EC
- explosion-proof luminaire
- exposure dose rate
- exposure limit
- externally illuminated exit sign
- externally reflected component (ERC)
- extraterrestrial solar illuminance constant
- extraterrestrial solar irradiance constant
- extraterrestrial solar radiation
- eye light
- f
- façade orientation
- fade
- fader
- far field
- FAY light
- fenestra method
- fenestration
- field angle
- field efficiency
- field lumens
- field of view (FOV)
- fill light
- film (or aperture) color
- filter
- filter (television, film, theater)
- finsen
- fiver (or five-K)
- fixed light
- fixed light equivalent
- fixture
- flag
- flash duration (on-period)
- flash frequency
- flash interval (off-period)
- flash period
- flashing light
- flashtube
- flicker fusion frequency, fff
- flicker index
- flicker photometer
- flood (television, film, theater)
- floodlight (exterior lighting)
- floodlight (television, film, theater)
- floodlighting
- floor cavity
- floor cavity ratio, FCR
- floor lamp
- floor pocket
- floren
- fluorescence
- fluorescent lamp
- flush mounted or recessed
- flux transfer theory
- fog (adverse weather) lamps
- follow spot (light)
- footcandle
- footcandle meter
- footlambert
- footlights
- form factor, f1 to 2
- formation light
- forward ray tracing
- fovea
- foveal vision
- Fresnel spotlight
- fringe light
- front lighting
- front of house (FOH) intercept panel
- front of house (FOH) spots
- funnel
- fuselage lights
- g
- gamut area index (GAI)
- gas-filled lamp
- gaseous discharge
- gel
- general color rendering index
- general diffuse lighting
- general illumination (television, film, theater)
- general lighting
- general lighting source lamp (GLS)
- general purpose floodlight, GP
- germicidal action spectrum
- germicidal dose
- germicidal effectiveness
- germicidal flux
- germicidal flux density
- germicidal lamp
- germicidal radiation
- ghost (or ghost load)
- glare
- global illuminance
- global solar radiation
- globe (for light control)
- globe (theater lighting equipment)
- gloss meter
- glossometer
- glow discharge
- glow factor
- glow lamp
- gobo
- goniophotometer
- graybody
- grid (or gridiron)
- grip
- grip gear
- ground-area open floodlight, O
- ground-area open floodlight with reflector insert, OI
- ground light
- ground row
- group control
- group flashing light
- h
- half scrim
- halo light
- halogen infrared (HIR)
- hand hole
- handheld remote
- hard cyc
- hard light
- hazard or obstruction beacon (aeronautical lighting)
- hazardous location
- haze factor
- headlamp
- headlight
- heat extraction thermal factor
- heavy duty floodlight, HD
- heliotherapy
- hemispherical-conical reflectance
- hemispherical-conical transmittance
- hemispherical-directional reflectance
- hemispherical-directional transmittance
- hemispherical reflectance*
- hemispherical transmittance*
- high-bay lighting
- high-end trim
- high hat
- high intensity discharge (HID) lamp
- high-key lighting
- high-mast lighting
- high pressure sodium (HPS) lamp
- horizontal exit
- horizontal plane of a searchlight
- horizontal shadow angle
- hot-cathode lamp
- house lights
- hue of a perceived color
- hybrid LED luminaire
- hydrargyrum medium arc length iodide (HMI) lamp
- i
- ice detection light
- ideal radiator
- identification beacon (aeronautical lighting)
- ignitor
- illuminance
- illuminance (lux or footcandle) meter
- illumination
- incandescence
- incandescent filament lamp
- incident angle
- incident dose (exposure dose)
- incomplete diffusion (partial diffusion)
- index of illuminant metamerism
- index of observer metamerism
- index of sensation, M
- indirect actinic effect (of optical radiation)
- indirect component
- indirect lighting
- infrared lamp
- infrared radiation
- inhibition
- initial luminous exitance
- inky
- instant-start fluorescent lamp
- institutional tuning
- instrument
- instrument schedule
- insulated glazing units
- integrated flash intensity
- integrating photometer
- integrating sphere
- intensity
- intensity (candlepower) distribution curve
- inter-lock
- interflectance method*
- internally illuminated exit sign
- internally reflected component (IRC)
- interreflected component
- interreflection
- interrupted quick-flashing light
- inverse-square law
- iris
- irradiance (E)
- isocandela line
- isolation transformer
- isoluminance line
- isolux (isofootcandle) line
- j
- Julian day
- junior
- k
- key light
- kicker
- klieg light
- Kosochmieder’s law
- l
- laboratory reference standard
- ladder
- lambert
- lambertian surface
- lambertian units of luminance
- Lambert’s cosine law
- laminated glass
- lamp
- lamp burnout factor
- lamp control
- lamp failure
- lamp lumen depreciation, LLD
- lamp position factor
- lamp post
- lamp shielding angle, ϕ
- landing direction indicator
- landing light
- landmark beacon
- laser
- lateral width of a light distribution
- law of reciprocity (Bunsen-Roscoe law)
- LED array or module
- LED control circuitry
- LED die
- LED driver
- LED driver, Class II
- LED lamp, integrated
- LED lamp, non-integrated
- LED light engine
- LED luminaire
- LED package
- LED power source
- LED power supply
- Leko
- lens
- level of illumination
- life of a test lamp
- life performance curve
- life test of lamps
- life test racks
- light
- light adaptation
- light center
- light center length (LCL)
- light emitting diode (LED)
- light lift
- light loss factor (LLF)
- light meter
- light output ratio
- light plot
- light shelf
- light source color
- light source description (for risk group classification)
- light-to-solar-gain ratio
- light trespass
- light well
- lighting-cooling index
- lighting effectiveness factor, LEF
- lighting power density (LPD)
- lighting system
- lighting zone (exterior lighting)
- lighting zone (interior lighting controls)
- lightness (of a perceived patch of surface color)
- linear light
- linear polarization
- Linnebach projector
- load shedding
- loader
- local lighting
- local solar time (LST)
- localized general lighting
- long-arc lamp
- longitudinal roadway line, LRL
- louver (or louver grid)
- louver shielding angle, θ
- louvered ceiling
- low-bay lighting
- low-e coating
- low-iron glass
- low-key lighting
- low pressure mercury lamp
- low pressure sodium (LPS) lamp
- lower (passing) beams
- lumen
- lumen depreciation compensation
- lumen maintenance control
- lumen (or flux) method
- lumen-second
- luminaire
- luminaire ambient temperature factor
- luminaire dirt depreciation, LDD
- luminaire efficiency
- luminaire spacing criterion, SC
- luminaire surface depreciation factor
- luminance
- luminance coefficient, LC
- luminance coefficient, q
- luminance contrast
- luminance contrast sensitivity
- luminance difference
- luminance difference threshold
- luminance factor, β
- luminance ratio
- luminance threshold
- luminescence
- luminous ceiling
- luminous efficacy of a source
- luminous efficacy of radiant flux
- luminous energy
- luminous exitance
- luminous fluence
- luminous fluence rate
- luminous flux
- luminous flux density at a surface
- luminous intensity
- luminous intensity distribution curve
- luminous range
- luminous reflectance
- luminous sterisent
- luminous transmittance
- lux
- lux meter
- m
- maintenance factor (MF)
- Martingale
- master
- matte
- matte surface
- mean horizontal intensity (candlepower)*
- mean spherical luminous intensity
- mean zonal candlepower
- means of egress
- median life
- memory
- mercury-fluorescent lamp (phosphor mercury lamp)
- mercury lamp
- mesopic vision
- message
- metal halide lamp
- metamers
- meteorological optical range
- midget
- Mie scatter
- miniblinds
- minimal perceptible erythema
- minimum erythemal dose
- MIRED
- modeling light
- modulation threshold
- monocular visual field
- motion detector
- mounting height, MH (interior)
- mounting height, MH (roadway)
- multilevel lighting control
- multiple-beam headlamp
- Munsell chroma
- Munsell color system
- Munsell hue
- Munsell value
- n
- nanometer (nm)
- narrow-angle diffusion
- narrow-angle luminaire
- national standard of light
- natural sky glow
- navigation light system
- near field
- networked lighting control system
- night
- nit (nt)
- nocturnal
- nominal range of a light signal
- non-dim circuit
- non-general lighting source lamp
- non-lens spotlight
- nonrecoverable light loss factor (initial or maintained)
- o
- Obie light
- object color
- obstruction beacon
- obstruction lights (aeronautical lighting)
- obtrusive light
- occulting light
- occupancy sensor
- olivette
- on-off ratio (or mark-space ratio) for a repeated single flash
- one-K
- opaque medium
- open-loop control
- optical radiation
- organic light emitting diode (OLED)
- orientation
- Ostwald color system
- overcast sky
- overhang
- overhead (or butterfly)
- ozone-producing radiation
- p
- paddle
- panel face exit sign
- pantograph
- PAR lamp
- par light
- parabolic spotlight
- parallel (television, film, theater)
- parking lamp
- partial diffusion
- partly cloudy sky
- passing beams
- patch
- patch panel
- pattern spotlight
- pendant luminaire
- perceived chroma of an area of surface color
- perceived color
- perceived light source color
- percent flicker
- Perez Sky Model
- perfect diffusion
- perimeter lights
- period life
- peripheral vision
- peripheral visual field
- personal tuning
- phantom
- phosphor mercury lamp
- phosphorescence
- phot-
- phot
- photobiological hazard
- photobiological (human) hazard function
- photobiology
- photocarcinogenesis
- photocataractogenesis
- photocell
- photochemical radiation
- photochemotherapy
- photochromic glazing
- photoconjunctivitis
- photocontrol
- photocuring
- photodynamic therapy
- photoeffect
- photoflash lamp
- photoflood lamp
- photokeratitis
- photokeratoconjunctivitis
- photometer
- photometric brightness
- photometry
- photomorphogenesis
- photomutagenesis
- photon
- photoperiod
- photoperiodism
- photopic vision
- photoretinitis
- photosensitization
- photosensor
- photosensor control algorithm
- photosynthesis
- photosynthetic irradiance
- photosynthetic photon flux density (PPFD)
- photosynthetically active radiation (PAR)
- phototaxis
- phototherapy
- phototropism
- physical photometer
- physical receptor
- pigtail
- pilot house control
- pin plug or connector
- pipe
- Planck radiation law
- Planckian locus
- plano-convex spotlight
- plate
- plot
- point brilliance, E
- point-by-point method
- point method
- point of fixation
- point of observation
- point source
- point vision
- polarization
- polarized radiation
- pole
- portable lighting
- portable luminaire
- portable traffic control light
- position index, P
- position lights
- practical lamp (television, film and theater)
- pre-burning time
- prefocus lamp
- preheat (switch start) fluorescent lamp
- preset
- pressed reflector lamp
- primary color
- primary daylight zone
- primary line of sight
- primary standard
- profile angle
- profile spotlight
- projection lamp
- projector
- protective lighting
- proximal stimulus
- psychometric chroma
- psychometric hue-angle
- psychometric lightness
- psychometric saturation
- public way
- pulsed lamp
- pupil (pupillary aperture)
- Purkinje phenomenon
- purple boundary
- q
- quality of lighting
- quantity of light (luminous energy, Q)
- quartz lights
- quartz (or quartz iodine, or quartz halogen)
- quick-flashing light
- r
- r-table
- radiance
- radiant efficiency
- radiant energy density
- radiant energy, Q
- radiant exitance
- radiant fluence
- radiant fluence rate
- radiant flux areal density
- radiant flux density at a surface
- radiant flux (radiant power)
- radiant intensity
- radiant sterisent
- radiator
- radiometry
- radiosity
- rail lights
- range lights
- rapid-start fluorescent lamp
- rated lamp life
- ray tracing
- Rayleigh scatter
- reaction time
- rear screen projector
- reciprocal color temperature
- reciprocity
- recoverable light loss factor
- redirecting surfaces and media
- reduced luminance coefficient, r
- reference ballast
- reference line
- reference standard
- reflectance factor, R
- reflectance, ρ (of a surface or medium)
- reflected direct luminaire
- reflected glare
- reflected radiation coefficient, RRC
- reflection
- reflective film
- reflectivity
- reflectometer
- reflector
- reflector lamp
- reflex reflector
- refraction
- refractor
- regions of the electromagnetic spectrum
- regressed
- regular (specular) reflectance
- regular (specular) reflection
- regulation (of voltage)
- relative contrast sensitivity, RCS
- relative luminosity
- relative luminosity factor
- relative photometry
- remote control switch
- resolving power
- resultant color shift
- retina
- retinal burn
- retinal burn hazard function
- retinal ganglion cells
- retinal hazard region
- retro-reflector (reflex reflector)
- rheostat
- rhythmic light
- ribbon filament lamp
- risk group 1 (low risk)
- risk group 2 (moderate risk)
- risk group 3 (high risk)
- risk group classification (of lamps)
- rods
- rooftop monitor
- room cavity
- room cavity ratio, RCR
- room coefficient,* Kr
- room index*
- room ratio*
- room surface dirt depreciation, RSDD
- room utilization factor (utilance)
- roundel
- runway alignment indicator
- runway centerline lights
- runway edge lights
- runway-end identification lights
- runway exit lights
- runway lights
- runway threshold
- runway visibility
- runway visual range, RVR
- s
- saturation of a perceived color
- sawtooth roof
- scene master
- scenic projector
- schedule (television, film, theater)
- scoop
- scotopic vision
- scrim
- scroller
- sealed beam headlamp
- sealed-beam lamp
- sealed beam spotlight
- searchlight
- seasoning
- seasoning time
- secondary daylight zone
- secondary standard
- self-ballasted lamps
- self-luminous exit sign
- semi-direct lighting
- semi-indirect lighting
- senior (television, film, theater)
- service period
- set light
- shade
- shading coefficient
- shielding angle (of a luminaire)
- short-arc (compact-arc) lamp
- shutters
- SI unit of luminance
- side-back light
- side light
- side marker lamps
- sidelighting
- signal shutter
- signaling light
- signaling system
- silicon controlled rectifier, SCR
- size threshold
- sky component (SC)
- sky glow
- sky illuminance
- sky light
- sky luminance distribution function
- sky luminance distribution models
- skylight
- snoot
- soft light
- solar altitude
- solar azimuth
- solar constant
- solar declination angle
- solar efficacy
- solar film
- solar heat gain coefficient (SHGC)
- solar illuminance constant
- solar time
- solarium
- solid angle
- solid angle factor, Q
- solid state lighting (SSL)
- spacing (roadway)
- spacing-to-mounting-height ratio, S/MH
- spatial daylight autonomy (sDA)
- special color rendering index
- specific illumination
- spectral-directional emissivity
- spectral-hemispherical emissivity
- spectral luminous efficacy of radiant flux
- spectral luminous efficiency for photopic vision
- spectral luminous efficiency for photopic vision, V(λ)
- spectral luminous efficiency for scotopic vision
- spectral luminous efficiency of radiant flux
- spectral power distribution (SPD)
- spectral radiance
- spectral radiant energy
- spectral radiant exitance and irradiance
- spectral radiant fluence
- spectral radiant fluence rate
- spectral radiant flux
- spectral radiant intensity
- spectral radiant sterisent
- spectral reflectance
- spectral (spectroscopic) lamp
- spectral-total directional emissivity
- spectral-total hemispherical emissivity
- spectral transmittance
- spectral transmittance distribution
- spectral tristimulus values
- spectral tuning
- spectrally selective glazing
- spectrophotometer
- spectroradiometer
- spectrum locus
- specular angle
- specular angle (direction) for transmission
- specular reflectance
- specular reflection
- specular surface
- specular transmission
- specular transmittance
- specularly reflective
- speed of light
- speed of vision
- sphere illuminance
- spherical reduction factor*
- spider
- spill light
- splay
- spot
- spotlight
- stabilization
- stabilization time
- stage manager’s panel
- stage plug
- standard erythemal dose
- standard illuminant
- standard illuminant A
- standard illuminant C
- standard illuminant D65
- standard source
- standard source A
- standard source C
- starter
- state of chromatic adaptation
- Stefan-Boltzmann law
- stencil face exit sign
- stilb
- Stiles-Crawford effect
- stop lamp
- stray light (in the eye)
- street lighting luminaire
- street lighting unit
- striplight (television, film and theater)
- stroboscopic lamp (strobe light)
- sub-master
- subjective brightness
- sun lamp
- sunburn
- sunlight
- suntan
- supplementary lighting
- supplementary standard illuminant D55
- supplementary standard illuminant D75
- surface mounted luminaire
- suspended (pendant) luminaire
- switch-start fluorescent lamp
- switchboard
- t
- table lamp
- Table T-1: Luminance Conversion Factors
- Table T-2: Standard Units, Symbols, and Defining Equations for Fundamental Photometric and Radiometric Quantities*
- Table T-3: Illuminance Conversion Factors
- Table T-4: Definitive Values of the Special Luminous Efficiency Function for Photopic Vision V(λ)
- Table T-5A: Color-Matching Functions and Chromaticity Coordinates of CIE 1931 Standard Colorimetric Observer
- Table T-5B: Color-Matching Functions and Chromaticity Coordinates of CIE 1964 Supplementary Standard Colorimetric Observer
- Table T-6: Relative Spectral Power Distribution of CIE Illuminant “C”
- Table T-7: Scotopic Spectral Luminous Efficiency Values, V′(λ) (Unity at Wavelength of Maximum Luminous Efficacy)
- Table T-8: Tentative Bactericidal Efficiency of Ultraviolet Radiation
- Table T-9: CIE 1988 Modified Two-Degree Spectral Lumnous Efficiency Function for Photopic Vision
- tail lamp
- talbot (T)
- tanning lamp
- task-ambient lighting
- task lighting
- task tuning
- taxi-channel lights
- taxi light
- taxiway centerline lights
- taxiway-edge lights
- taxiway holding-post light
- taxiway lights
- temperature radiator
- tenner (or ten-K, or 10-K)
- thermochromic glazing
- threshold
- threshold increment (TI)
- threshold lights
- throw
- time switch
- timeclock
- tonal light
- top hat
- top light
- toplighting
- torchère (or torchiere)
- tormentor lighting
- total emissivity
- total internal reflection (TIR)
- total (solar) radiation
- total solar radiation
- total spectral radiant flux
- touchdown zone lights
- track lighting
- traffic beams
- train
- transient adaptation factor, TAF
- transillumination
- transition lighting
- translucent
- translucent insulating panels
- translucent medium
- transmission
- transmissometer
- transmittance (of a medium)
- transparent medium
- transverse roadway line, TRL
- tristimulus values of a light, X,Y,Z
- troffer
- troland
- Troxler effect
- tube
- tubular daylighting device (TDD)
- tunable lighting
- tungsten-halogen lamp
- turn-signal operating unit
- two-K
- twofer
- u
- U-factor
- U.S. Customary System (USCS, formerly English) unit of luminance
- ultraviolet hazard function
- ultraviolet lamp
- ultraviolet radiation
- ultraviolet subdivisions
- unified glare rating, UGR
- unilateral sidelighting
- unit (lighting equipment)
- units of luminous exitance
- units of wavelength
- unrecoverable light loss factor
- upper (driving) beams
- upward component
- useful daylight illuminance (UDI)
- v
- vacancy sensor
- vacuum lamp
- valance
- valance lighting
- vapor-tight luminaire
- VASIS
- veiling brightness
- veiling luminance
- veiling reflection
- venetian blinds
- vertical blinds
- vertical plane of a searchlight
- vertical shadow angle
- very short flashes
- view window
- visibility
- visibility level, VL
- visibility (meteorological)
- visibility performance criteria function, VL8
- visibility reference function, VL1
- visible transmittance
- vision
- visual acuity
- visual angle
- Visual Approach Slope Indicator System (VASIS)
- visual comfort probability, VCP
- visual field
- visual perception
- visual performance
- visual photometer
- visual range (of a light or object)
- visual signal
- visual surround
- visual task
- visual task evaluator (VTE)
- visual threshold in point vision
- voltage to luminaire factor
- w
- wall direct radiation coefficient, WDRC
- wall pocket
- wall reflected radiation coefficient, WRRC
- warm-up time
- wash
- Weber's fraction
- wide-angle diffusion
- wide-angle luminaire
- width line
- Wien displacement law
- Wien radiation law
- window
- window sash
- window shades
- wing clearance lights
- work light
- work plane
- working standard
- wrong way “law”
- y
- Y-cord
- z
- zenith
- zonal cavity coefficients
- zonal cavity interreflectance method
- zonal constant
- zonal factor interflection method*
- zonal factor method
- zonal multipliers