Same word as visa:

acceptance, accepting, accord, admission, affirmation, affirming, agreement, approval, assent, attestation, authenticating, authentication, authorization, authorizing, avowal, consent, corroborating, corroboration, endorsement, evidence, go ahead, green light, nod, okay, passage, passing, proving, recognition, sanction, sanctioning, stamp of approval, substantiation, support, supporting, testament, testimonial, testimony, validating, verification, verifying, visa, witness