theoretician vs intellectual

theoretician and intellectual both are nouns.

Word	Noun	Adjective	Verb	Adverb
theoretician	Yes	No	No	No
intellectual	Yes	Yes	No	No

As nouns, intellectual is a hypernym of theoretician; that is, intellectual is a word with a broader meaning than theoretician:

Other hypernyms of theoretician include intellect.

theoretician (noun)	intellectual (noun)
someone who theorizes (especially in science or art)	a person who uses the mind creatively

theoretician (adjective)	intellectual (adjective)
	appealing to or using the intellect
	involving intelligence rather than emotions or instinct
	of or associated with or requiring the use of the mind