Corroborative describes information that supports or helps to prove someone else’s statement, idea, or result. Corroborative evidence is the extra backing: another witness, a document, a recording, a second test. The word is formal and a little old-fashioned in tone; many writers now just say supporting evidence. You will still meet it in law and in careful academic prose. It is an adjective, so it sits in front of a noun (corroborative testimony, corroborative findings). Though actually, English also has a rare noun use for a thing that corroborates, but students can ignore that — the adjective is the one you will see. It has nothing to do with collaborative, which is about working as a team.

佐證的；起證實作用的