determinant

(noun) a determining or causal element or factor. Synonyms: determiner, determinative, determining factor, causal factor. Example: "Education is an important determinant of one's outlook on life."

(noun) the site on the surface of an antigen molecule to which an antibody attaches itself. Synonyms: antigenic determinant, epitope.

(noun) a square matrix used to solve simultaneous equations.

(adj) having the power or quality of deciding. Synonyms: deciding(prenominal), determinative, determining(prenominal). Examples: "The crucial experiment." "Cast the deciding vote." "The determinative (or determinant) battle."