observer
n. countablen. someone who watches or notices something carefully. It can also mean a person who is sent to a meeting or event to watch what happens without taking part.
n. a person who watches or notices something; alternatively, a representative sent to witness proceedings without participating officially. Often used in political or scientific contexts to describe a neutral party.
The observer watched the birds from a distance.
International observers arrived at the polling stations to ensure the election was conducted fairly and transparently.
To a casual observer, the two paintings might look identical, but a trained eye can easily spot the subtle differences in brushwork and color saturation.
From observe + -er.
Often followed by the preposition 'of' when describing someone who watches a specific event or phenomenon.