-ic

CIDE DICTIONARY

-ic,  [L. -icus, Gr. : cf. F. -ique.].

•  A suffix signifying, in general, relating to, or characteristic of; as, historic, hygienic, telegraphic, etc.  [1913 Webster]
•  A suffix, denoting that the element indicated enters into certain compounds with its highest valence, or with a valence relatively higher than in compounds where the name of the element ends in -ous; as, ferric, sulphuric. It is also used in the general sense of pertaining to; as, hydric, sodic, calcic.  [1913 Webster]

OXFORD DICTIONARY

-ic, suffix.
1 forming adjectives (Arabic; classic; public) and nouns (critic; epic; mechanic; music).
2 Chem. in higher valence or degree of oxidation (ferric; sulphuric) (see also -OUS).
3 denoting a particular form or instance of a noun in -ics (aesthetic; tactic).

Etymology

from or after F -ique or L -icus or Gk -ikos: cf. -ATIC, -ETIC, -FIC, -OTIC