word-forming element meaning "all," from Latin omni-, combining form of omnis "all, every, the whole, of every kind," a word of unknown origin, perhaps literally "abundant," from *op-ni-, from PIE root *op- "to work, produce in abundance."

also homoeo-, word-forming element meaning "similar to," Latinized from Greek homio-, from homoios "like, resembling, of the same kind; equal," related to or an expanded form of homos "one and the same" (from PIE root *sem- (1) "one; as one, together with").

word-forming element used since 18c. (but most productively in 20c.), "kind of, like but not really, as if," expressing some resemblance but implying a degree of fictitious or unreal quality or lack of some important feature; from Latin quasi "as if, as it were" (see quasi).

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).