multilateralism (n.)

also multi-lateral, 1690s, in geometry, "having many sides," from multi- "many" + lateral (adj.). Figurative use, "many-sided," is by 1748. Meaning "pertaining to three or more countries" is from 1802 (based on bilateral). Related: Multilaterally.

word-forming element making nouns implying a practice, system, doctrine, etc., from French -isme or directly from Latin -isma, -ismus (source also of Italian, Spanish -ismo, Dutch, German -ismus), from Greek -ismos, noun ending signifying the practice or teaching of a thing, from the stem of verbs in -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached. For distinction of use, see -ity. The related Greek suffix -isma(t)- affects some forms.