equation

Etymology

From Old French, from Latin aequātiō (“an equalizing”). Morphologically equate + -ion

noun

1. The act or process of equating two or more things, or the state of those things being equal (that is, identical).
   We need to bring the balance of power into equation
   The cultural equation of love with suffering is similar to the equation of love with an experience of both transcendence and consummation in which love is affirmed in an ostentatious display of self loss. 2013, Eva Illouz, Why Love Hurts: A Sociological Explanation
2. (mathematics) 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.
3. (astronomy) A small correction to observed values to remove the effects of systematic errors in an observation.