sedan vs sedan chair

sedan and sedan chair both are nouns.

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

As nouns, sedan and sedan chair are synonyms defined as:

sedan (noun)	sedan chair (noun)
a car that is closed and that has front and rear seats and two or four doors	a closed litter for one passenger
a closed litter for one passenger