stop number vs f number

stop number and f number both are nouns.

Word	Noun	Adjective	Verb	Adverb
stop number	Yes	No	No	No
f number	Yes	No	No	No

As nouns, stop number and f number are synonyms defined as:

stop number and f number: the ratio of the focal length to the diameter of a (camera) lens system

Other synonyms of stop number include focal ratio, speed.

stop number (noun)	f number (noun)
the ratio of the focal length to the diameter of a (camera) lens system	the ratio of the focal length to the diameter of a (camera) lens system