bi·na·ry (b??n?-r?) adj. 1. Characterized by or consisting of two parts or components; twofold. 2. a. Of or relating to a system of numeration having 2 as its base. b. Of or relating to a system of encoding data using only 0’s and 1’s. 3. Chemistry Consisting of or containing only two kinds of atoms. 4. Of or employing two comparatively nontoxic chemicals that combine to produce a deadly poison: binary weapons; a binary nerve agent. 5. Music Having two sections or subjects. n. pl. bi·na·ries 1. A number system having 2 as its base. 2. A file that contains the executable version of a computer program. 3. A binary star. [Middle English binarie, from Late Latin b?n?rius, from Latin b?n?, two by two; see dwo- in the Appendix of Indo-European roots.] American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.binary (?ba?n?r?) adj1. composed of, relating to, or involving two; dual2. (Mathematics) maths computing of, relating to, or expressed in binary notation or binary code3. (Chemistry) (of a compound or molecule) containing atoms of two different elements4. (Metallurgy) metallurgy (of an alloy) consisting of two components or phases5. (Education) (of an educational system) consisting of two parallel forms of education such as the grammar school and the secondary modern in Britain6. (Mathematics) maths logic (of a relation, expression, or operation) applying to two elements of its domain; having two argument places; dyadicn, pl -ries7. something composed of two parts or things8. (Astronomy) astronomy See binary star9. (Military) short for binary weapon[C16: from Late Latin b?n?rius; see bin-]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014bi?na?ry (?ba? n? ri, -n?r i) adj., n., pl. -ries. adj. 1. consisting of, indicating, or involving two. 2. a. of or pertaining 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. b. of or pertaining to the digits or numbers used in binary notation. c. of or pertaining to a binary system. 3. noting a chemical compound containing only two elements or groups, as sodium chloride or methyl bromide. 4. of, pertaining to, or involving a relationship between two alternatives existing in opposition to each other. n. 5. a whole composed of two. 6. binary star. 7. Also called bi?nary num?ber. a number expressed in the binary system of notation. [1350?1400; Middle English