breathalyser vs breathalyzer

breathalyser and breathalyzer both are nouns.

Word	Noun	Adjective	Verb	Adverb
breathalyser	Yes	No	No	No
breathalyzer	Yes	No	No	No

As nouns, breathalyser and breathalyzer are synonyms defined as:

breathalyser and breathalyzer: a device that measures chemicals (especially the alcohol content) in a person's expired breath

breathalyser (noun)	breathalyzer (noun)
a device that measures chemicals (especially the alcohol content) in a person's expired breath	a device that measures chemicals (especially the alcohol content) in a person's expired breath