synthesise vs synthesiser

synthesise is not a noun while synthesiser is a noun.

Word	Noun	Adjective	Verb	Adverb
synthesise	No	No	Yes	No
synthesiser	Yes	No	No	No

synthesise (noun)	synthesiser (noun)
	(music) an electronic instrument (usually played with a keyboard) that generates and modifies sounds electronically and can imitate a variety of other musical instruments
	an intellectual who synthesizes or uses synthetic methods

synthesise (verb)	synthesiser (verb)
combine so as to form a more complex, product