diapason stop vs diapason

diapason stop and diapason both are nouns.

Word	Noun	Adjective	Verb	Adverb
diapason stop	Yes	No	No	No
diapason	Yes	No	No	No

As nouns, diapason stop and diapason are synonyms defined as:

diapason stop and diapason: either of the two main stops on a pipe organ

diapason stop (noun)	diapason (noun)
either of the two main stops on a pipe organ	either of the two main stops on a pipe organ