truck vs garbage truck

truck and garbage truck both are nouns.

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

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

truck (noun)	garbage truck (noun)
an automotive vehicle suitable for hauling	a truck for collecting domestic refuse
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

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