word-forming element meaning "many, much, multi-, one or more," from Greek polys "much" (plural polloi), from PIE root *pele- (1) "to fill," with derivatives referring to multitudinousness or abundance. Equivalent to Latin multi-, it is properly used in compounds only with words of Greek origin. In chemical names, usually indicating a compound with a large number of atoms or molecules of the same kind (such as polymer).

1780, "condition of having many wives, marriage or cohabitation of one man with more than one woman at the same time," from Greek polygynēs "having many wives," from polys "many" (see poly-) + gynē "woman, wife" (from PIE root *gwen- "woman"). Related: Polygynous.

"marriage within the tribe or group," 1865, from endo- on model of polygamy. Related: Endogamous (1865). Opposed to exogamy. Apparently both were coined by Scottish anthropologist John Ferguson McLennan (1827-1881) in "Primitive Marriage."

To this law, the converse of caste, forbidding marriage within the tribe, Mr. M'Lennan has given the name of exogamy: while, instead of caste, since that word involves notions unconnected with marriage, he has used the correlative word — endogamy. [review in The Lancet, March 25, 1865]

"relating to or characterized by polygamy," especially in reference to a marriage including more than one spouse of either sex, 1610s, from polygamy + -ous, or else from Late Greek polygamos "often married." In zoology, "mating with more than one individual." Related: Polygamously.