Definitions:
an algebraic expression of the sum or the difference of two terms.

a two-part name, especially the latin name of a species of living organism (consisting of the genus followed by the specific epithet).

a noun phrase with two heads joined by a conjunction, in which the order is relatively fixed (as in knife and fork).

consisting of two terms.

having or using two names (used especially of the latin name of a species of living organism).