I. adjective 1. relating to, composed of, or involving two things. 2. relating to, using, or denoting a system of numerical notation that has 2 rather than 10 as a base. II. noun 1. [ mass noun] — the binary system of notation. • the device is counting in binary.
2. something having two parts. 3. a binary star.
– origin late Middle English (in the sense ‘duality, a pair’): from late Latin binarius, from bini ‘two together’.