string tie vs necktie

string tie and necktie both are nouns.

Word	Noun	Adjective	Verb	Adverb
string tie	Yes	No	No	No
necktie	Yes	No	No	No

As nouns, necktie is a hypernym of string tie; that is, necktie is a word with a broader meaning than string tie:

string tie: a very narrow necktie usually tied in a bow
necktie: neckwear consisting of a long narrow piece of material worn (mostly by men) under a collar and tied in knot at the front

Other hypernyms of string tie include tie.

string tie (noun)	necktie (noun)
a very narrow necktie usually tied in a bow	neckwear consisting of a long narrow piece of material worn (mostly by men) under a collar and tied in knot at the front