unary (adj.)

Proto-Indo-European root meaning "one, unique."

It forms all or part of: a (1) indefinite article; alone; an; Angus; anon; atone; any; eleven; inch (n.1) "linear measure, one-twelfth of a foot;" lone; lonely; non-; none; null; once; one; ounce (n.1) unit of weight; quincunx; triune; unanimous; unary; une; uni-; Uniate; unilateral; uncial; unicorn; union; unique; unison; unite; unity; universal; universe; university; zollverein.

It is the hypothetical source of/evidence for its existence is provided by: Greek oinos "ace (on dice);" Latin unus "one;" Old Persian aivam; Old Church Slavonic -inu, ino-; Lithuanian vienas; Old Irish oin; Breton un "one;" Old English an, German ein, Gothic ains "one."

"dual, twofold, double," 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" (from PIE root *dwo- "two"). Binary code in computer terminology was in use by 1952, though the idea itself is ancient. Binary star in astronomy is from 1802.