sustainability (n.)

1610s, "bearable," a sense now obsolete, from sustain + -able. Attested from 1845 in the sense "defensible, capable of being upheld;" by 1965 with the meaning "capable of being continued at a certain level;" sustainable growth also is recorded from 1965. Related: Sustainably.

word-forming element making abstract nouns from adjectives and meaning "condition or quality of being ______," from Middle English -ite, from Old French -ete (Modern French -ité) and directly from Latin -itatem (nominative -itas), suffix denoting state or condition, composed of -i- (from the stem or else a connective) + the common abstract suffix -tas (see -ty (2)).

Roughly, the word in -ity usually means the quality of being what the adjective describes, or concretely an instance of the quality, or collectively all the instances; & the word in -ism means the disposition, or collectively all those who feel it. [Fowler]