a suffix forming adjectives from other parts of speech, occurring originally in Greek and Latin loanwords (metallic; poetic; archaic; public) and, on this model, used as an adjective-forming suffix with the particular senses “having some characteristics of” (opposed to the simple attributive use of the base noun) (balletic; sophomoric); “in the style of” (Byronic; Miltonic); “pertaining to a family of peoples or languages” (Finnic; Semitic; Turkic).
Chemistry. a suffix, specialized in opposition to -ous, used to show the higher of two valences: ferric chloride.
a noun suffix occurring chiefly in loanwords from Greek, where such words were originally adjectival (critic; magic; music).
Origin of -ic
Middle English-ic, -ik < Latin-icus; in many words representing the cognate Greek-ikos (directly or through L); in some words replacing -ique < French < Latin-icus
adjective suffix, "having to do with, having the nature of, being, made of, caused by, similar to" (in chemistry, indicating a higher valence than names in -ous), from French -ique and directly from Latin -icus, which in many cases represents Greek -ikos "in the manner of; pertaining to." From PIE *-(i)ko, which also yielded Slavic -isku, adjectival suffix indicating origin, the source of the -sky (Russian -skii) in many surnames.