Why is the ninth month called September?
late 14c., from Old French comunité "community, commonness, everybody" (Modern French communauté), from Latin communitatem (nominative communitas) "community, society, fellowship, friendly intercourse; courtesy, condescension, affability," from communis "common, public, general, shared by all or many," (see common (adj.)). Latin communitatem "was merely a noun of quality ... meaning 'fellowship, community of relations or feelings,' but in med.L. it was, like universitas, used concretely in the sense of 'a body of fellows or fellow-townsmen' " [OED].
An Old English word for "community" was gemænscipe "community, fellowship, union, common ownership," from mæne "common, public, general," probably composed from the same PIE roots as communis. Community service as a criminal sentence is recorded from 1972, American English. Community college is recorded from 1959.
A group of organisms or populations living and interacting with one another in a particular environment. The organisms in a community affect each other's abundance, distribution, and evolutionary adaptation. Depending on how broadly one views the interaction between organisms, a community can be small and local, as in a pond or tree, or regional or global, as in a biome.