a person or thing that views.

a person who watches television, often a devotee of television or of a particular kind of television program

a weekly show aimed at teenage viewers.

any of various optical devices to facilitate viewing, esp. one that is small and boxlike with a magnifying lens, and sometimes a light source, in which a photographic transparency may be viewed.

an eyepiece or viewfinder.

an official inspector of property, public works, or the like.

noun

eyewitness , seer