-ic 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).