CONFIRMATIVE

collateral, confirmative, confirming, confirmatory, corroborative, corroboratory, substantiating, substantiative, validating, validatory, verificatory, verifying

(adjective) serving to support or corroborate; “collateral evidence”

Source: WordNet® 3.1

Etymology

Adjective

confirmative (comparative more confirmative, superlative most confirmative)

That serves to confirm

Source: Wiktionary

Con*firm"a*tive, a. Etym: [L. confirmativus: cf. F. confirmatif.]

Definition: Tending confirm or establish. Sherwood.

– Con*firm"a*tive*ly, adv.

Source: Webster’s Unabridged Dictionary 1913 Edition