ETYM AS. witness, gewitnes, from witan to know. Related to Wit.
1. A person who attests to the genuineness of a document or signature by adding their own signature; SYN. attestant.
2. Someone who sees an event and tells what happened; SYN. informant.
3. Testimony by word or deed to one's religious faith.
In law, a person who was present at some event (such as an accident, a crime, or the signing of a document) or has relevant special knowledge (such as a medical expert) and can be called on to give evidence in a court of law.

1. To be a witness to.
2. To perceive with any or all of one's senses; give rise to or be characterized by; SYN. find, see.