studio apartment vs apartment

studio apartment and apartment both are nouns.

Word	Noun	Adjective	Verb	Adverb
studio apartment	Yes	No	No	No
apartment	Yes	No	No	No

As nouns, apartment is a hypernym of studio apartment; that is, apartment is a word with a broader meaning than studio apartment:

studio apartment: an apartment with a living space and a bathroom and a small kitchen
apartment: a suite of rooms usually on one floor of an apartment house

Other hypernyms of studio apartment include flat.

studio apartment (noun)	apartment (noun)
an apartment with a living space and a bathroom and a small kitchen	a suite of rooms usually on one floor of an apartment house