ter·na·ry (tûr?n?-r?)adj.1. Composed of three or arranged in threes.2. Mathematics a. Having the base three.b. Involving three variables.n. pl. ter·na·ries A group of three.[Middle English, from Latin tern?rius, from tern?, three each; see tern2.]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.ternary (?t??n?r?) adj1. consisting of three or groups of three2. (Mathematics) maths a. (of a number system) to the base threeb. involving or containing three variables3. (Chemistry) (of an alloy, mixture, or chemical compound) having three different components or composed of three different elementsn, pl -riesa group of three[C14: from Latin tern?rius, from tern? three each]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ter?na?ry (?t?r n? ri) adj., n., pl. -ries. adj. 1. consisting of or involving three; threefold; triple. 2. third in order or rank. 3. based on the number three. 4. a. consisting of three different chemical elements or groups. b. (formerly) consisting of three atoms. 5. Math. having three variables. n. 6. a group of three. [1400?50; late Middle English