- plein air,
- pleiotropic gene,
also pleo-, word-forming element meaning "more," from comb. form of Greek pleion "larger, greater in quantity, the more part, very many" (comp. of polys "much"), from PIE *ple- (cf. Latin plere "to fill," plebes, "the populace, the common people;" Greek plethein "be full," pleres "full"), possibly a variant of *pele- (1) "to fill" (see poly-).