fire truck vs truck

fire truck and truck both are nouns.

Word	Noun	Adjective	Verb	Adverb
fire truck	Yes	No	No	No
truck	Yes	No	Yes	No

As nouns, truck is a hypernym of fire truck; that is, truck is a word with a broader meaning than fire truck:

fire truck: any of various large trucks that carry firemen and equipment to the site of a fire
truck: an automotive vehicle suitable for hauling

Other hypernyms of fire truck include motortruck.

fire truck (noun)	truck (noun)
any of various large trucks that carry firemen and equipment to the site of a fire	an automotive vehicle suitable for hauling
	a handcart that has a frame with two low wheels and a ledge at the bottom and handles at the top; used to move crates or other heavy objects

fire truck (verb)	truck (verb)
	convey (goods etc.) by truck