an optical device for viewing photographic transparencies
"He placed the slide in the viewer to examine the details of his vacation photos."
Someone who views a spectacle; an onlooker or spectator.
"The crowd watched in silence as the fireworks lit up the night sky, every viewer captivated by the dazzling display."
In plain English: A viewer is someone who watches something, usually on television or online.
"Many viewers watched the popular movie during its premiere night."
Usage: Use viewer to describe someone watching a specific event, performance, or broadcast rather than general audiences like spectators or fans. It often implies a focused observation of something presented visually, such as in art galleries or live streams.
The word viewer comes from Middle English and is formed by adding the suffix "-er" to the verb "view." It originally meant a person who views something, retaining that same meaning in modern English.