derby vs derby hat

derby and derby hat both are nouns.

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

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

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

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

derby (noun)	derby 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