n.1 the process of equating or making equal; the state of being equal.
2 Math. a statement that two mathematical expressions are equal (indicated by the sign ).
3 Chem. a formula indicating a chemical reaction by means of symbols for the elements taking part.
Phrases and idioms:
equation of the first order, second order , etc. an equation involving only the first derivative, second derivative, etc.
Derivatives:
equational adj.
Etymology: ME f. OF equation or L aequatio (as EQUATE)