knife vs trench knife

knife and trench knife both are nouns.

Word	Noun	Adjective	Verb	Adverb
knife	Yes	No	Yes	No
trench knife	Yes	No	No	No

As nouns, trench knife is a hyponym of knife; that is, trench knife is a word with a more specific, narrower meaning than knife:

Other hyponyms of knife include bayonet, dagger, sticker, khukuri, machete, matchet, panga, shiv, yataghan, kindjal, seax.

knife (noun)	trench knife (noun)
edge tool used as a cutting instrument; has a pointed blade with a sharp edge and a handle	a knife with a double-edged blade for hand-to-hand fighting
a weapon with a handle and blade with a sharp point
any long thin projection that is transient

knife (verb)	trench knife (verb)
use a knife on