derby vs bowler hat

derby and bowler hat both are nouns.

Word	Noun	Adjective	Verb	Adverb
derby	Yes	No	No	No
bowler hat	Yes	No	No	No

As nouns, derby and bowler hat are synonyms defined as:

derby and bowler hat: a felt hat that is round and hard with a narrow brim

Other synonyms of derby include bowler, derby hat, plug hat.

derby (noun)	bowler hat (noun)
a felt hat that is round and hard with a narrow brim	a felt hat that is round and hard with a narrow brim