synthesise vs synthesize

synthesise and synthesize both are verbs.

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

As verbs, synthesise and synthesize are synonyms defined as:

synthesise and synthesize: combine so as to form a more complex, product

synthesise (verb)	synthesize (verb)
combine so as to form a more complex, product	combine so as to form a more complex, product
	combine and form a synthesis