The word "witness" refers to someone who sees or experiences an event, often with their own eyes or senses. A witness can provide important information or evidence about what happened during that event. Full definition
Like many others of the time (and probably yours, too), my elementary school classroom was decorated with a cloud of witnesses of sorts. (relevantmagazine.com)
It is often challenging to prove fault, and you may require the assistance of expert witnesses in order to do so. (tengelaw.com)
They often provide services as expert witnesses in order to discuss a victim's future rehabilitation needs, as well as the costs associated with such treatment. (jrlawfirm.com)