duplex house vs semidetached house

duplex house and semidetached house both are nouns.

Word	Noun	Adjective	Verb	Adverb
duplex house	Yes	No	No	No
semidetached house	Yes	No	No	No

As nouns, duplex house and semidetached house are synonyms defined as:

duplex house and semidetached house: a house with two units sharing a common wall

Other synonyms of duplex house include duplex.

duplex house (noun)	semidetached house (noun)
a house with two units sharing a common wall	a house with two units sharing a common wall