-ics

WordReference Random House Learner's Dictionary of American English © 2025

-ics, suffix. 

1. Pronouns -ics is attached to roots to form nouns with the meaning "a body of facts, knowledge, or principles.'' Such nouns usually correspond to adjectives ending in -icor-ical:
   eth- (= custom;
   character) + -ics → ethics (= the principles of good character).

WordReference Random House Unabridged Dictionary of American English © 2025

-ics, 

1. Pronouns 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.

• Greek -ika, neuter plural of -ikos), as in rhētórica (plural) rhetoric book
• plural of -ic, representing Latin -ica (

Usage

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.

ICS, 

1. International College of Surgeons.

Collins Concise English Dictionary © HarperCollins Publishers::

-ics suffix:forming_nouns (functioning as singular)

1. indicating a science, art, or matters relating to a particular subject: aeronautics, politics
2. indicating certain activities or practices: acrobatics

Etymology: plural of -ic, representing Latin -ica, from Greek -ika, as in mathēmatika mathematics