sedan vs brougham

sedan and brougham both are nouns.

Word	Noun	Adjective	Verb	Adverb
sedan	Yes	No	No	No
brougham	Yes	No	No	No

As nouns, brougham is a hyponym of sedan; that is, brougham is a word with a more specific, narrower meaning than sedan:

sedan: a car that is closed and that has front and rear seats and two or four doors
brougham: a sedan that has no roof over the driver's seat

sedan (noun)	brougham (noun)
a car that is closed and that has front and rear seats and two or four doors	a sedan that has no roof over the driver's seat
a closed litter for one passenger	light carriage; pulled by a single horse