-ics

1.
a suffix of nouns that denote a body of facts, knowledge, principles, etc., usually corresponding to adjectives ending in -ic, or -ical: ethics; physics; politics; tactics .
Origin
plural of -ic, representing Latin -ica (< Greek -ika, neuter plural of -ikos), as in rhētórica (plural) rhetoric book
Usage note
Nouns ending in -ics that name fields of study, sciences, arts, professions, or the like are usually not preceded by an article and are used with a singular verb: Acoustics (the science) deals with sound. Politics (the art of government) fascinates me. In certain uses, often when preceded by a determiner like the, his, her, or their, most of these nouns can take a plural verb: The acoustics (the sound-reflecting qualities) of the hall are splendid. Their politics (political opinions) have antagonized everyone.
British Dictionary definitions for -ics

-ics

suffix (functioning as sing)
1.
indicating a science, art, or matters relating to a particular subject: aeronautics, politics
2.
indicating certain activities or practices: acrobatics
Word Origin
plural of -ic, representing Latin -ica, from Greek -ika, as in mathēmatika mathematics
Word Origin and History for -ics

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 (e.g. arithmetic, logic).

-ics in Medicine

-ics suff.

  1. Science; art; study; knowledge; skill: pharmaceutics.

  2. Actions, activities, or practices of: macrobiotics.