observer Definition

observe
verb observed, observing

1. To notice or become conscious of something.

Thesaurus: notice, perceive, see, view, witness; Antonym: miss, overlook.
2. To watch something carefully; to pay close attention to it.

Thesaurus: watch, examine, inspect, scrutinize, keep an eye on, monitor.
tr & intr
3. To examine and note (behaviour, symptoms or phenomena, etc).
4. To obey, follow or keep (a law, custom or religious rite, etc).

Thesaurus: commemorate, celebrate, solemnize, dedicate, honour, remember, follow, heed, keep, mind, obey, abide by, respect, adhere to, comply, conform to, fulfill;.
tr & intr
5. To make a remark or comment.

Example: observed that he was late again
Thesaurus: comment, note, remark, mention.

Derivative: observable
adj

Able to be noticed or perceived
Thesaurus: evident, discernible, obvious, noticeable, perceptible, perceivable, visible, recognizable, apparent, appreciable, detectable, measurable; Antonym: hidden, obscure.

Derivative: observably
adverb

Derivative: observer
noun

Someone who watches or sees something
Thesaurus: spectator, bystander, eyewitness, onlooker, witness, watcher, sentinel, guard, lookout, sentry, policeman, spy, voyeur, peeping Tom.

Etymology: 14c: from Latin observare, from ob- towards + servare to keep or watch.