self-organization vs self-organisation

self-organization and self-organisation both are nouns.

Word	Noun	Adjective	Verb	Adverb
self-organization	Yes	No	No	No
self-organisation	Yes	No	No	No

As nouns, self-organization and self-organisation are synonyms defined as:

self-organization and self-organisation: organizing yourself (especially organizing your own labor union)

self-organization (noun)	self-organisation (noun)
organizing yourself (especially organizing your own labor union)	organizing yourself (especially organizing your own labor union)