The IES defines illumination engineering terms in ANSI/IES LS-1-22, 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-1-22 on these pages:
Copyright, Disclaimer, and American National Standards Statement
Foreword, Nomenclature Committee members, Introduction, and Scope
- tenner (or ten-K, or 10-K)
- threshold
- threshold increment (TI)
- threshold lights
- throw
- time switch
- tint
- tonal light
- tone
- top hat
- top light
- toplighting
- torchère (or torchiere)
- tormentor lighting
- total emissivity
- total internal reflection (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
- trichromacy
- tristimulus values of a light, X,Y,Z
- troffer
- troland
- Troxler effect
- tube
- tunable lighting
- tunable white
- tungsten-halogen lamp
- turn-signal operating unit
- two-K
- twofer
- U.S. Customary System (USCS, formerly English) unit of luminance
- ultraviolet germicidal irradiation (UVGI)
- ultraviolet germicidal lamp
- ultraviolet hazard function
- ultraviolet lamp
- ultraviolet radiation
- ultraviolet subdivisions
- unified glare rating, UGR
- uniform chromaticity scale diagram (UCS)
- unilateral sidelighting
- unit (lighting equipment)
- units of luminous exitance
- units of wavelength
- univariance
- unrecoverable light loss factor
- upper (driving) beams
- upward component
- vacancy sensor
- vacuum lamp
- valance
- valance lighting
- value
- 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
- wall direct radiation coefficient, WDRC
- wall pocket
- wall reflected radiation coefficient, WRRC
- warm-up time
- wash
- Weber’s fraction
- wide-angle diffusion