Absolute Humidity - Refers to the mass of water in a particular volume of air. Absolute humidity is expressed as the number of kilograms of water vapor per cubic meter of air.

Anemometer - A device for measuring airflow or the pressure of moving air. The term is derived from the Greek word "anemos" meaning wind.

Candela - The luminous intensity, in a given direction, of a source that emits monochromatic radiation with wavelengths weighted to the standardized model of sensitivity of the human eye.

Carbon Dioxide - A chemical compound composed of one carbon and two oxygen atoms. It is often referred to by its chemical formula CO2 (the "2" is subscript).

Carbon Monoxide - A toxic, colorless, odorless, and tasteless gas. It consists of one carbon atom covalently bonded to one oxygen atom and has the chemical formula CO.

cd - Candela

Celsius (formerly Centigrade) - A thermometric scale in which the freezing point of water is 0°C and its boiling point 100°C at normal sea level atmospheric pressure (14.7 psi). °C = (°F-32)/1.8.

CO - Carbon Monoxide

CO2 - Carbon Dioxide

Data Logger - An electronic instrument that records data over time

dB - Decibel

Decibel - A measure of the ratio between two quantities, and is used in a wide variety of measurements in acoustics, physics and electronics. The decibel is widely used in measurements of the loudness of sound.

Dew Point - The temperature at which a given parcel of air must be cooled at a constant barometric pressure for water vapor to condense into water.

DS - Distance to spot

Emissivity - Usually written e, is the ratio of energy radiated to energy absorbed by a black body at the same temperature. It is a measure of a material's ability to absorb and radiate energy. A true black body would have an e = 1 while any real object would have e < 1. This emissivity depends on factors such as temperature, emission angle, and wavelength. However, a typical engineering assumption is to assume that a surface's spectral emissivity does not depend on wavelength, so that the emissivity is a constant. This is known as the grey body assumption. When dealing with non-black surfaces, the deviations from ideal black body behavior are determined by both the geometrical structure and the chemical composition.

Fahrenheit - A thermometric scale in which 32°F denotes freezing and 212°F the boiling point of water under normal sea level atmospheric pressure of 14.7 psi. °F = (1.8°xC) + 32.

fc - Footcandle

Footcandle - Can also be called as luminance per square foot is a standard unit of luminance. It is "the illuminance cast on a surface by a one-candela source one foot away". 1fc is approximately equal to 10.764lux

Heat - The energy that an object has because of its temperature. Heat is different from temperature (q.v.) because an object with twice as much mass requires twice as much heat to increase its temperature by the same amount.

HSL - Hue, Saturation, Luminance

IAQ - Indoor Air Quality

Indoor Air Quality - The quality or composition of interior air that could affect health and/or comfort of a building's contents or occupants.

Infrared Radiation - Form of electromagnetic radiation with a wavelength between 0.7 and 100 micrometers (µm).

IR - Infrared radiation

lm - Lumen

Lumen - Is the unit of measurement of luminous flux which is the perceived power of light.

lux - The lux symbol is lx and is a standard unit of luminance. It is used in photometry as a measure of the perceived intensity of light. 1lx is approximately equal to 0.0929fc.

lx - Lux

OSHA - Occupational Safety and Health Administration is an agency of the United States Department of Labor. Its mission is to prevent work-related injuries, illnesses, and deaths by issuing and enforcing rules (called standards) for workplace safety and health.

pH - A measure of the acidity or basicity of a measurable substance. Substances with a pH less than seven are considered acidic, while those with a pH greater than seven are considered basic (or alkaline). pH 7 is defined as neutral, because it is the pH level of pure water at 25 °C.

Relative Humidity - The ratio of the current vapor pressure of water in any gas (especially air), known as the absolute vapor pressure, to the equilibrium vapor pressure or saturation vapor pressure, at which the gas is called saturated at the current temperature, expressed as a percentage.

RGB - The RGB color model is an additive model in which red, green and blue (often used in additive light models) are combined in various ways to reproduce other colors. The name of the model and the abbreviation "RGB" comes from the three primary colors, Red, Green and Blue.

RH - Relative humidity

Temperature - What a thermometer measures. Temperature is the average kinetic energy per molecule.

Thermocouple - In electronics, thermocouples are a widely used type of temperature sensor and can also be used as a means to convert thermal potential difference into electric potential difference. They are cheap, interchangeable, have standard connectors, and can measure a wide range of temperatures. The main limitation is accuracy; system errors of less than 1 °C can be difficult to achieve.