The IES defines illumination engineering terms in ANSI/IES RP-16, 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 RP-16 on these pages:
Copyright, Disclaimer, and American National Standards Statement
Foreword, Nomenclature Committee members, Introduction, and Scope
Spectral Parameters Used in Illumination Engineering
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a
- Abbe’s law
- absolute luminance threshold
- 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
- amalgam
- ambient lighting
- analog multiplex, AMX
- anchor light
- angle-of-approach lights
- angle of collimation
- Annex A - Physical Receptors and Devices
- 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
- asbestos tapoff
- astronomical time clock
- atmospheric transmissivity
- 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
- 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
- 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
- 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 standard chromaticity diagram
- circadian
- circling guidance lights
- clear sky
- clearance lamps
- clerestory
- 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 of a physical stimulus
- 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
- 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
- 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 availability
- daylight conversion filter
- daylight factor
- daylight lamp
- densitometer
- designer’s remote
- deuce
- dichroic filter
- diffuse reflectance
- diffuse reflection
- diffuse sky radiation
- diffuse transmission
- diffuse transmittance
- diffused lighting
- 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 ratio
- 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 stimuli
- 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
- dummy load
- dust-proof luminaire
- dust-tight luminaire
- Dutchman
- duty cycle
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
- electrodeless fluorescent lamp
- electroluminescence
- electromagnetic spectrum
- elevation
- ellipsoidal reflector spotlight
- emergency exit
- emergency lighting
- emissivity
- emittance
- enclosed and gasketed luminaire
- equal interval (isophase) light
- 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
- eye light
f
- fade
- fader
- far field
- FAY light
- fenestra method
- fenestration
- field angle
- field efficiency
- field lumens
- 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
- flick interval
- flick-scint
- 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)
- ganglion cells
- 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 solar radiation
- globe (for light control)
- globe (theater lighting equipment)
- 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
- 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 hat
- high intensity discharge (HID) lamp
- high-key lighting
- high-mast lighting
- high pressure sodium (HPS) lamp
- horizontal exit
- horizontal plane of a searchlight
- 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 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
- instrument
- instrument schedule
- integrated flash intensity
- integrating photometer
- integrating sphere
- intensity
- intensity (candlepower) distribution curve
- inter-lock
- interflectance method*
- internally illuminated exit sign
- interreflected component
- interreflection
- interrupted quick-flashing light
- inverse-square law
- iris
- irradiance (E)
- isocandela line
- isolation transformer
- isoluminance line
- isolux (isofootcandle) line
j
- 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
- 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
- latitude
- 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 source color
- light source description (for risk group classification)
- light trespass
- lighting-cooling index
- lighting effectiveness factor, LEF
- lighting zone (exterior lighting)
- lighting zone (interior lighting controls)
- lightness (of a perceived patch of surface color)
- linear light
- linear polarization
- Linnebach projector
- loader
- local lighting
- localized general lighting
- long-arc lamp
- longitude
- longitudinal roadway line, LRL
- louver (or louver grid)
- louver shielding angle, θ
- louvered ceiling
- low-bay lighting
- low-key lighting
- low pressure mercury lamp
- low pressure sodium (LPS) lamp
- lower (passing) beams
- lumen
- 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 contrast
- luminance contrast sensitivity
- luminance difference
- luminance difference threshold
- luminance factor, β
- luminance ratio
- luminance threshold
- luminescence
- luminous ceiling
- luminous density
- luminous efficacy of a source of light
- 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
- minimal perceptible erythema
- minimum erythemal dose
- MIRED
- modeling light
- modulation threshold
- monocular visual field
- motion detector
- mounting height, MH (interior)
- mounting height, MH (roadway)
- multiflick flash
- 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
- navigation light system
- near field
- 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)
- occulting light
- occupancy sensor
- olivette
- on-off ratio (or mark-space ratio) for a repeated single flash
- one-K
- opaque medium
- 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
- 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
- photochemical radiation
- photochemotherapy
- 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
- photosynthesis
- photosynthetic irradiance
- photosynthetic photon flux density (PPFD)
- photosynthetically active radiation (PAR)
- phototaxis
- phototherapy
- phototropism
- physical photometer
- physical receptor
- physical stimuli
- 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
- primary line of sight
- primary standard
- profile angle
- profile spotlight
- projection lamp
- projector
- protective lighting
- proximal stimuli
- 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
- 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
- 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
- reflectivity
- reflectometer
- reflector
- reflector lamp
- reflex reflector
- refraction
- refractor
- regions of the electromagnetic spectrum
- regressed
- regular (specular) reflectance
- regular (specular) reflection
- regular transmission
- regular transmittance
- regulation (of voltage)
- relative contrast sensitivity, RCS
- relative luminosity
- relative luminosity factor
- remote control switch
- resolving power
- resultant color shift
- retina
- retinal burn
- retinal burn hazard function
- 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
- 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
- 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 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
- signal shutter
- signaling light
- signaling system
- silicon controlled rectifier, SCR
- size threshold
- sky factor
- sky light
- sky luminance distribution function
- skylight
- snoot
- soft light
- solar constant
- solar efficacy
- solar illuminance constant
- solar radiation simulator
- solarium
- solid angle
- solid angle factor, Q
- 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 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 tristimulus values
- spectral tuning
- spectrophotometer
- spectroradiometer
- spectrum locus
- specular angle
- specular reflectance
- specular reflection
- specular surface
- speed of light
- speed of vision
- sphere illuminance
- spherical reduction factor*
- spider
- 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 bearing
- 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)
- threshold
- threshold increment (TI)
- threshold lights
- throw
- time clock
- tonal light
- top hat
- top light
- toplighting
- torchère (or torchiere)
- tormentor lighting
- total emissivity
- total internal reflectance, TIR
- total (solar) radiation
- touchdown zone lights
- track lighting
- traffic beams
- train
- transient adaptation factor, TAF
- transillumination
- transition lighting
- 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
- tunable lighting
- tungsten-halogen
- tungsten-halogen lamp
- turn-signal operating unit
- two-K
- twofer
u
- 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
v
- vacancy sensor
- vacuum lamp
- valance
- valance lighting
- vapor-tight luminaire
- VASIS
- veiling brightness
- veiling luminance
- veiling reflection
- vertical plane of a searchlight
- very short flashes
- 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
- wing clearance lights
- work light
- work plane
- working standard
- wrong way “law”
y
- Y-cord
z
- zonal cavity coefficients
- zonal cavity interreflectance method
- zonal constant
- zonal factor interflection method*
- zonal factor method
- zonal multipliers