nucleolus organiser vs nucleolus organizer

nucleolus organiser and nucleolus organizer both are nouns.

Word	Noun	Adjective	Verb	Adverb
nucleolus organiser	Yes	No	No	No
nucleolus organizer	Yes	No	No	No

As nouns, nucleolus organiser and nucleolus organizer are synonyms defined as:

nucleolus organiser and nucleolus organizer: the particular part of a chromosome that is associated with a nucleolus after nuclear division

Other synonyms of nucleolus organiser include nucleolar organiser, nucleolar organizer.

nucleolus organiser (noun)	nucleolus organizer (noun)
the particular part of a chromosome that is associated with a nucleolus after nuclear division	the particular part of a chromosome that is associated with a nucleolus after nuclear division