nucleolar organizer vs nucleolus organiser

nucleolar organizer and nucleolus organiser both are nouns.

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

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

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

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

nucleolar 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