observer vs motile

observer and motile both are nouns.

Word	Noun	Adjective	Verb	Adverb
observer	Yes	No	No	No
motile	Yes	Yes	No	No

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

observer: a person who becomes aware (of things or events) through the senses
motile: one whose prevailing mental imagery takes the form of inner feelings of action

observer (noun)	motile (noun)
a person who becomes aware (of things or events) through the senses	one whose prevailing mental imagery takes the form of inner feelings of action
an expert who observes and comments on something

observer (adjective)	motile (adjective)
	(of spores or microorganisms) capable of movement