freight vs charge per unit

freight and charge per unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
freight	Yes	No	Yes	No
charge per unit	Yes	No	No	No

As nouns, charge per unit is a hypernym of freight; that is, charge per unit is a word with a broader meaning than freight:

Other hypernyms of freight include rate.

freight (noun)	charge per unit (noun)
transporting goods commercially at rates cheaper than express rates	amount of a charge or payment relative to some basis
goods carried by a large vehicle
the charge for transporting something by common carrier

freight (verb)	charge per unit (verb)
load with goods for transportation
transport commercially as cargo