nucleolar organiser vs nucleolar organizer

nucleolar organiser and nucleolar organizer both are nouns.

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

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

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

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

nucleolar organiser (noun)	nucleolar 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