Also ‑ick, ‑ique, ‑ical, and ‑icity.
Forming adjectives and some nouns.
French ‑ique, Latin ‑icus, or Greek ‑ikos.
A very large number of adjectives in ‑ic exist, of which a few examples are aquatic, bucolic, chronic, drastic, electric, heroic, and terrific.
In chemistry, the ‑ic ending forms adjectives indicating an element in a higher valency compared with a form ending in ‑ous: cupric, ferric, nitric, sulphuric.
Some examples, though principally adjectives, can also be nouns (cosmetic, lunatic, lyric); some are now primarily nouns (arithmetic, mechanic, mimic, picnic, sceptic), though a number can also act as adjectives. Some noun examples mark a particular instance of a noun in ‑ics (aesthetic, ethic, mnemonic, statistic, tactic).
Nouns in ‑ic often have linked adjectives in ‑ical (lyrical, tactical). Many other examples of adjectives with this ending exist, such as chemical, farcical, practical, and vertical. In many cases both forms exist (classic and classical; historic and historical); sometimes these have slightly different senses, but often they are interchangeable (comic or comical; geographic or geographical; symmetric or symmetrical) and the choice is often personal, or set by a house style, or to suit the rhythm of the sentence.
The ending ‑icity forms abstract nouns indicating a quality or condition (authenticity, electricity, toxicity).
The spelling ‑ick (Gothick, musick) is now archaic or deliberately used as an archaism. A few words retain the French spelling in ‑ique (mystique, physique, unique).