decameter vs decametre

decameter and decametre both are nouns.

Word	Noun	Adjective	Verb	Adverb
decameter	Yes	No	No	No
decametre	Yes	No	No	No

As nouns, decameter and decametre are synonyms defined as:

Other synonyms of decameter include dam, dekameter, dekametre, dkm.

decameter (noun)	decametre (noun)
a metric unit of length equal to ten meters	a metric unit of length equal to ten meters