nucleolus organizer vs nucleolus organiser

nucleolus organizer and nucleolus organiser both are nouns.

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

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

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

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

nucleolus organizer (noun)	nucleolus organiser (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