kilometers per hour vs km/h

kilometers per hour and km/h both are nouns.

Word	Noun	Adjective	Verb	Adverb
kilometers per hour	Yes	No	No	No
km/h	Yes	No	No	No

As nouns, kilometers per hour and km/h are synonyms defined as:

kilometers per hour and km/h: the ratio of the distance traveled (in kilometers) to the time spent traveling (in hours)

Other synonyms of kilometers per hour include kilometres per hour, kph.

kilometers per hour (noun)	km/h (noun)
the ratio of the distance traveled (in kilometers) to the time spent traveling (in hours)	the ratio of the distance traveled (in kilometers) to the time spent traveling (in hours)