Noun viewer has 2 senses
  1. spectator, witness, viewer, watcher, looker - a close observer; someone who looks at something (such as an exhibition of some kind); "the spectators applauded the performance"; "television viewers"; "sky watchers discovered a new star"
    --1 is a kind of perceiver, observer, beholder
    --1 has particulars:
     browser; bystander; cheerer; eyewitness; moviegoer, motion-picture fan; ogler; onlooker, looker-on; playgoer, theatergoer, theatregoer; rubberneck; spy; starer; voyeur, Peeping Tom, peeper
    Derived form: verb view3
  2. viewer - an optical device for viewing photographic transparencies
    --2 is a kind of
    optical device
    Derived form: verb view2
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