witness

One who can give a firsthand account of something seen, heard, or experienced.

One who is called on to testify before a court.

One who is called on to be present at a transaction in order to attest to what takes place.

One who signs one’s name to a document for the purpose of attesting to its authenticity.

Attestation to a fact, statement, or event; testimony.

Something that serves as evidence; a sign.

One who publicly affirms religious faith.