kilometre vs kilometer

kilometre and kilometer both are nouns.

Word	Noun	Adjective	Verb	Adverb
kilometre	Yes	No	No	No
kilometer	Yes	No	No	No

As nouns, kilometre and kilometer are synonyms defined as:

kilometre and kilometer: a metric unit of length equal to 1000 meters (or 0.621371 miles)

Other synonyms of kilometre include klick, km.

kilometre (noun)	kilometer (noun)
a metric unit of length equal to 1000 meters (or 0.621371 miles)	a metric unit of length equal to 1000 meters (or 0.621371 miles)