Klavier vs stringed instrument

Klavier and stringed instrument both are nouns.

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

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

Klavier: a stringed instrument that has a keyboard
stringed instrument: a musical instrument in which taut strings provide the source of sound

Other hypernyms of Klavier include keyboard instrument.

Klavier (noun)	stringed instrument (noun)
a stringed instrument that has a keyboard	a musical instrument in which taut strings provide the source of sound