(1):

(a.) Consisting of two terms; pertaining to binomials; as, a binomial root.

(2):

(a.) Having two names; - used of the system by which every animal and plant receives two names, the one indicating the genus, the other the species, to which it belongs.

(3):

(n.) An expression consisting of two terms connected by the sign plus (+) or minus (-); as, a + b, or 7 - 3.