1. Comprising two components, elements, molecules, etc. 2. Denoting a choice of two mutually exclusive outcomes for one event ( e.g., male or female, heads or tails, affected or unaffected). [L. binarius, consisting of two, fr. bini, two at a time]
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bi·na·ry 'bī-nə-rē, -.ner-ē adj
1) compounded or consisting of or marked by two things or parts
2 a) composed of two chemical elements, an element and a radical that acts as an element, or two such radicals
b) utilizing two harmless ingredients that upon combining form a lethal substance (as a gas)
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bi·na·ry (biґnə-re) [L. binarius of two] 1. made up of two elements. 2. denoting a number system with a base of two.Medical dictionary. 2011.