1. A number indicating the amount of some change under certain specified conditions, often expressed as a ratio.
For example, the coefficient of linear expansion of a substance is the ratio of its change in length to the original length for a unit change of temperature from a standard.
2. A constant in an algebraic equation.
3. One of several parts which combine to make a whole, as the maximum deviation produced by each of several causes.
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use