dulcimer vs stringed instrument

dulcimer and stringed instrument both are nouns.

Word	Noun	Adjective	Verb	Adverb
dulcimer	Yes	No	No	No
stringed instrument	Yes	No	No	No

As nouns, stringed instrument is a hypernym of dulcimer; that is, stringed instrument is a word with a broader meaning than dulcimer:

dulcimer: a stringed instrument used in American folk music; an elliptical body and a fretted fingerboard and three strings
stringed instrument: a musical instrument in which taut strings provide the source of sound

dulcimer (noun)	stringed instrument (noun)
a trapezoidal zither whose metal strings are struck with light hammers	a musical instrument in which taut strings provide the source of sound
a stringed instrument used in American folk music; an elliptical body and a fretted fingerboard and three strings