1530s, "one's proper work or purpose; power of acting in a specific proper way," from French fonction (16c.) and directly from Latin functionem (nominative functio) "a performance, an execution," noun of action from funct-, past-participle stem of fungi "perform, execute, discharge," from PIE *bhung- "be of use, be used" (source also of Sanskrit bhunjate "to benefit, make benefit, atone," Armenian bowcanem "to feed," Old Irish bongaid "to break, harvest"), which is perhaps related to root *bhrug- "to enjoy." Meaning "official ceremony" is from 1630s, originally in church use. Use in mathematics probably was begun by Leibnitz (1692). In reference to computer operations, 1947.
late 14c., "round, having the form of a circle," from Anglo-French circuler, Old French circuler "circular" (14c., Modern French circulaire), from Latin circularis, from circulus "small ring" (see circle (n.)). Meaning "intended for circulation" is from 1650s. The metaphoric circular firing squad is attested by 1990.
1550s, "circular figure," from circular (adj.). Meaning "a notice circulated, a printed paper intended for general circulation" is from 1818, short for circular letter (1650s), one directed to a certain circle of persons and addressing a common interest.
1844, "perform a function" (intransitive), from function (n.). Related: Functioned; functioning.
"round, circular, spherical, having the shape of an orb," mid-15c., from Old French orbiculaire "round, circular," or directly from Late Latin orbicularis "circular, orbicular," from Latin orbiculus, diminutive of orbis "circle" (see orb). Related: Orbicularity.