a.

1. 二元的；二进位的；由二部分构成的

n.

1. 一双，一对；双体
2. 二进制数
3. 双子星

adj.

1. composed of or involving two things.
2. using or denoting a system of numerical notation with two as its base, employing the digits 0 and 1.

n.

1. the binary system of notation.
2. Astronomy  a system of two stars revolving round their common centre.