tonne-kilometer vs American spelling

tonne-kilometer and American spelling both are nouns.

Word	Noun	Adjective	Verb	Adverb
tonne-kilometer	Yes	No	No	No
American spelling	Yes	No	No	No

tonne-kilometer (noun)	American spelling (noun)
a unit of measure used in freight transport which determines the transport of one tonne of goods by a transport mode over one kilometer.	English orthography used in the United States (characterized by 'analyze', 'center', 'usable')