contractor vs hauler

contractor and hauler both are nouns.

Word	Noun	Adjective	Verb	Adverb
contractor	Yes	No	No	No
hauler	Yes	No	No	No

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

Other hyponyms of contractor include defense contractor, haulier, ship-breaker, subcontractor.

contractor (noun)	hauler (noun)
a bodily organ that contracts	a haulage contractor
someone (a person or firm) who contracts to build things
(law) a party to a contract
the bridge player in contract bridge who wins the bidding and can declare which suit is to be trumps