fact vs observation

fact and observation both are nouns.

Word	Noun	Adjective	Verb	Adverb
fact	Yes	No	No	No
observation	Yes	No	No	No

As nouns, observation is a hyponym of fact; that is, observation is a word with a more specific, narrower meaning than fact:

fact: a piece of information about circumstances that exist or events that have occurred
observation: facts learned by observing

Other hyponyms of fact include case, detail, item, point, particular, specific, general, matter of fact, reason, score, truth.

fact (noun)	observation (noun)
a piece of information about circumstances that exist or events that have occurred	the act of observing; taking a patient look
a concept whose truth can be proved	the act of making and recording a measurement
a statement or assertion of verified information about something that is the case or has happened	the act of noticing or paying attention
an event known to have happened or something known to have existed	facts learned by observing
	a remark expressing careful consideration