derby hat vs bowler hat

derby hat and bowler hat both are nouns.

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

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

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

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

derby hat (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