observe vs watch

observe is not a noun while watch is a noun.

Word	Noun	Adjective	Verb	Adverb
observe	No	No	Yes	No
watch	Yes	No	Yes	No

As verbs, watch is a hypernym of observe; that is, watch is a word with a broader meaning than observe:

As verbs, observe and watch are synonyms defined as:

Other synonyms of observe include follow, keep an eye on, watch over.

observe (noun)	watch (noun)
	a purposeful surveillance to guard or observe
	the rite of staying awake for devotional purposes (especially on the eve of a religious festival)
	a small portable timepiece
	a person employed to keep watch for some anticipated event
	a period of time (4 or 2 hours) during which some of a ship's crew are on duty
	the period during which someone (especially a guard) is on duty

observe (verb)	watch (verb)
stick to correctly or closely	find out, learn, or determine with certainty, usually by making an inquiry or other effort
make mention of	look attentively
watch attentively	be vigilant, be on the lookout or be careful
observe with care or pay close attention to	observe without intervening
discover or determine the existence, presence, or fact of by perception with the eyes	observe or determine by looking
follow with the eyes or the mind	see or watch
show respect towards	follow with the eyes or the mind
behave as expected during of holidays or rites
conform one's action or practice to