semantics n.

"relating to significance or meaning," 1894, from French sémantique, applied by Michel Bréal (1883) to the psychology of language, from Greek sēmantikos "significant," from sēmainein "to show by sign, signify, point out, indicate by a sign," from sēma "sign, mark, token; omen, portent; constellation; grave" (Doric sama), from PIE root *dheie- "to see, look" (source also of Sanskrit dhyati "he meditates;" see zen).

The word has tended to become loose in application. Semanticize "invest (something) with meaning; analyze semantically" is by 1942.

in the names of sciences or disciplines (acoustics, aerobics, economics, etc.), a 16c. revival of the classical custom of using the neuter plural of adjectives with Greek -ikos "pertaining to" (see -ic) to mean "matters relevant to" and also as the titles of treatises about them. Subject matters that acquired their English names before c. 1500, however, tend to be singular in form (arithmetic, logic, magic, music, rhetoric). The grammatical number of words in -ics (mathematics is/mathematics are) is a confused question.