subpart vs portion

subpart and portion both are nouns.

Word	Noun	Adjective	Verb	Adverb
subpart	Yes	No	No	No
portion	Yes	No	Yes	No

As nouns, portion is a hypernym of subpart; that is, portion is a word with a broader meaning than subpart:

Other hypernyms of subpart include component, component part, constituent, part.

subpart (noun)	portion (noun)
a part of a part	the allotment of some amount by dividing something
	something less than the whole of a human artifact
	an individual quantity of food or drink taken as part of a meal
	assets belonging to or due to or contributed by an individual person or group
	money or property brought by a woman to her husband at marriage
	something determined in relation to something that includes it
	your overall circumstances or condition in life (including everything that happens to you)

subpart (verb)	portion (verb)
	give out