cupboard vs closet

cupboard and closet both are nouns.

Word	Noun	Adjective	Verb	Adverb
cupboard	Yes	No	No	No
closet	Yes	No	Yes	No

As nouns, cupboard and closet are synonyms defined as:

cupboard and closet: a small room (or recess) or cabinet used for storage space

cupboard (noun)	closet (noun)
a small room (or recess) or cabinet used for storage space	a small private room for study or prayer
	a toilet in Britain
	a tall piece of furniture that provides storage space for clothes; has a door and rails or hooks for hanging clothes
	a small room (or recess) or cabinet used for storage space

cupboard (verb)	closet (verb)
	confine to a small space, as for intensive work