fluoridation vs fluoridisation

fluoridation and fluoridisation both are nouns.

Word	Noun	Adjective	Verb	Adverb
fluoridation	Yes	No	No	No
fluoridisation	Yes	No	No	No

As nouns, fluoridation and fluoridisation are synonyms defined as:

fluoridation and fluoridisation: the addition of a fluoride to the water supply (to prevent dental decay)

Other synonyms of fluoridation include fluoridization.

fluoridation (noun)	fluoridisation (noun)
the addition of a fluoride to the water supply (to prevent dental decay)	the addition of a fluoride to the water supply (to prevent dental decay)