wardrobe vs piece of furniture

wardrobe and piece of furniture both are nouns.

Word	Noun	Adjective	Verb	Adverb
wardrobe	Yes	No	No	No
piece of furniture	Yes	No	No	No

As nouns, piece of furniture is a hypernym of wardrobe; that is, piece of furniture is a word with a broader meaning than wardrobe:

wardrobe: a tall piece of furniture that provides storage space for clothes; has a door and rails or hooks for hanging clothes
piece of furniture: furnishings that make a room or other area ready for occupancy

Other hypernyms of wardrobe include article of furniture, furniture.

wardrobe (noun)	piece of furniture (noun)
a tall piece of furniture that provides storage space for clothes; has a door and rails or hooks for hanging clothes	furnishings that make a room or other area ready for occupancy
collection of clothing belonging to one person
collection of costumes belonging to a theatrical company