guitar vs stringed instrument

guitar and stringed instrument both are nouns.

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

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

guitar: a stringed instrument usually having six strings; played by strumming or plucking
stringed instrument: a musical instrument in which taut strings provide the source of sound

guitar (noun)	stringed instrument (noun)
a stringed instrument usually having six strings; played by strumming or plucking	a musical instrument in which taut strings provide the source of sound