-icsyoudaoicibaDictYouDict[-ics 词源字典]
in the names of sciences or disciplines (acoustics, aerobics, economics, etc.) it represents a 16c. revival of the classical custom of using the neuter plural of adjectives with -ikos (see -ic) to mean "matters relevant to" and also as the titles of treatises about them. Subject matters that acquired their names in English before c. 1500, however, tend to remain in singular (such as arithmetic, logic).[-ics etymology, -ics origin, 英语词源]