harmonica vs mouth harp

harmonica and mouth harp both are nouns.

Word	Noun	Adjective	Verb	Adverb
harmonica	Yes	No	No	No
mouth harp	Yes	No	No	No

As nouns, harmonica and mouth harp are synonyms defined as:

harmonica and mouth harp: a small rectangular free-reed instrument having a row of free reeds set back in air holes and played by blowing into the desired hole

Other synonyms of harmonica include harp, mouth organ.

harmonica (noun)	mouth harp (noun)
a small rectangular free-reed instrument having a row of free reeds set back in air holes and played by blowing into the desired hole	a small rectangular free-reed instrument having a row of free reeds set back in air holes and played by blowing into the desired hole