maisonette vs apartment

maisonette and apartment both are nouns.

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

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

maisonette: a self-contained apartment (usually on two floors) in a larger house and with its own entrance from the outside
apartment: a suite of rooms usually on one floor of an apartment house

Other hypernyms of maisonette include flat.

maisonette (noun)	apartment (noun)
a small house	a suite of rooms usually on one floor of an apartment house
a self-contained apartment (usually on two floors) in a larger house and with its own entrance from the outside