compass vs cotton on

compass is a noun but cotton on is not a noun.

Word	Noun	Adjective	Verb	Adverb
compass	Yes	No	Yes	No
cotton on	No	No	Yes	No

As verbs, cotton on is a hyponym of compass; that is, cotton on is a word with a more specific, narrower meaning than compass:

Other hyponyms of compass include figure, catch on, get it, get onto, get wise, latch on, tumble, twig, intuit, digest.

compass (noun)	cotton on (noun)
navigational instrument for finding directions
drafting instrument used for drawing circles
an area in which something acts or operates or has power or control:
the limit of capability

compass (verb)	cotton on (verb)
get the meaning of something	understand, usually after some initial difficulty
travel around, either by plane or ship
bring about; accomplish