specialiser vs specializer

specialiser and specializer both are nouns.

Word	Noun	Adjective	Verb	Adverb
specialiser	Yes	No	No	No
specializer	Yes	No	No	No

As nouns, specialiser and specializer are synonyms defined as:

specialiser and specializer: an expert who is devoted to one occupation or branch of learning

Other synonyms of specialiser include specialist.

specialiser (noun)	specializer (noun)
an expert who is devoted to one occupation or branch of learning	an expert who is devoted to one occupation or branch of learning