coefficient-¹ [MATH] A number or algebraic symbol prefixed as a multiplier to a variable or unknown quantity. ² [PHYSICS] A number, constant for a given substance, used as a multiplier; e.g., the coefficient of expansion.

coefficient of thermal expansion—The relative change (expansion or contraction), expressed as a ratio, in a linear dimension of a material body corresponding to a change of 1° in the temperature of the body. May be expressed in terms of Centigrade, Fahrenheit, or other thermometer units. Its magnitude depends on the material: a steel tape has a coefficient of expansion about 25 times as great as that of an Invar tape. It is usually expressed as a decimal fraction, and in a measure of distance, as of a base line, enters as a correction which is a product of the coefficient of expansion of the length apparatus, the distance measured, and the difference between the temperature at which the measure was made and the temperature at which the length of the apparatus is known.

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Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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