of or relating to a system of numerical notation to the base 2, in which each place of a number, expressed as 0 or 1, corresponds to a power of 2. The decimal number 58 appears as 111010 in binary notation, since 58 = 1 × 25 + 1 × 24 + 1 × 23 + 0 × 22 + 1 × 21 + 0 × 20.

of or relating to the digits or numbers used in binary notation.

(of an operation) assigning a third quantity to two given quantities, as in the addition of two numbers.

Computers. of, relating to, or written in binary code; programmed or encoded using only the digits 0 and 1: All executable programs on the computer are stored in binary files.

Chemistry. noting a compound containing only two elements or groups, as sodium chloride, methyl bromide, or methyl hydroxide.

Metallurgy. (of an alloy) having two principal constituents.

noun,pluralbi·na·ries.

a whole composed of two.

Mathematics. a system of numerical notation to the base 2, in which each place of a number, expressed as 0 or 1, corresponds to a power of 2: to convert decimal to binary.

Also called binary number. Mathematics. a number expressed in the binary system of notation.

"dual," mid-15c., from Late Latin binarius "consisting of two," from bini "twofold, two apiece, two-by-two" (used especially of matched things), from bis "double" (see bis-). Binary code in computer terminology was in use by 1952, though the idea itself is ancient. Binary star in astronomy is from 1802.

Anything composed of two parts. In modern computers, information is stored in banks of components that act like switches. Since switches can be either on or off, they have a binary character, and we say that the computer uses “binary arithmetic” to do its work.