guess vs opine

guess is a noun but opine is not a noun.

Word	Noun	Adjective	Verb	Adverb
guess	Yes	No	Yes	No
opine	No	No	Yes	No

As verbs, guess and opine are synonyms defined as:

Other synonyms of guess include imagine, reckon, suppose, think.

guess (noun)	opine (noun)
an estimate based on little or no information
a message expressing an opinion based on incomplete evidence

guess (verb)	opine (verb)
expect, believe, or suppose	expect, believe, or suppose
judge tentatively or form an estimate of (quantities or time)	express one's opinion openly and without fear or hesitation
guess correctly; solve by guessing
put forward, of a guess, in spite of possible refutation