The act or process of equating two or more things, or the state of those things being equal (that is, identical).
An assertion that two expressions are equal, expressed by writing the two expressions separated by an equal sign; from which one is to determine a particular quantity.
A small correction to observed values to remove the effects of systematic errors in an observation.
The act of measuring.
Value (quantity, magnitude, extent or amount) determined by an act of measuring.