word-forming element meaning "rule," from Latin -archia, from Greek -arkhia "rule," from arkhos "leader, chief, ruler," from arkhē "beginning, origin, first place," verbal noun of arkhein "to be the first," hence "to begin" and "to rule" (see archon).
"rule by numerical majority," 1850, from Greek arithmos "number, counting, amount" (see arithmetic) + -cracy "rule or government by." Related: Arithmocratic; arithmocratical.
late 13c., regnen, "to hold or exercise sovereign or royal power in a state," also of God, Christ, the Virgin Mary, from Old French regner "rule, reign" (12c.), from Latin regnare "have royal power, be king, rule, reign," from regnum "kingship, dominion, rule, realm," which is related to regere "to rule, to direct, keep straight, guide" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule"). Of customs, vices, etc. in a particular place, early 14c. Related: Reigned; reigning; regnal.
late 14c., "not subject to (a rule, law, authority, etc.)," from Old French exempt (13c.) and directly from Latin exemptus, past participle of eximere "remove, take out, take away; free, release, deliver, make an exception of," from ex "out" (see ex-) + emere "to buy," originally "to take," from PIE root *em- "to take, distribute." Also in Middle English in a more general sense, "taken away, cut off (from), removed (from)."
late 14c., "government, rule, authority, control," a sense now obsolete, from Old French regiment "government, rule" (14c.), from Late Latin regimentum "rule, direction," from Latin regere "to rule, to direct, keep straight, guide" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule").
The military meaning "unit of an army" is recorded by 1570s, from a sense in French; the reference in the word originally was to permanent organization and discipline. The exact number of soldiers in a regiment has varied widely over time and place.