PC vs portable computer

PC and portable computer both are nouns.

Word	Noun	Adjective	Verb	Adverb
PC	Yes	No	No	No
portable computer	Yes	No	No	No

As nouns, portable computer is a hyponym of PC; that is, portable computer is a word with a more specific, narrower meaning than PC:

PC: a small digital computer based on a microprocessor and designed to be used by one person at a time
portable computer: a personal computer that can easily be carried by hand

Other hyponyms of PC include desktop computer.

PC (noun)	portable computer (noun)
a small digital computer based on a microprocessor and designed to be used by one person at a time	a personal computer that can easily be carried by hand