Witness
Onlooker
Synonyms: Observer, looker-on, spectator, watcher, passer-by, onlooker, eyewitness, viewer, bystander, and earwitness.
Proof
Observe
Synonyms: See, watch, be a witness to, note, spot, attend, observe, look on at, view, notice, be present at, and behold.
Endorse
Synonyms: Countersign, endorse, certificate, notarize, sign, validate, and document.
Example Sentences
I will witness the event tomorrow.
She was a witness to history.
He hoped to witness the sunrise.
They called a witness to testify.