f number fnma • fo · · · Info · Definitions · Synonyms · Characters · · f number · · Text Common · · Latin · · Scripts 8 · · Length 3 · · Syllables Definitions · · · (noun) the ratio of the focal length to the diameter of a (camera) lens system. Synonyms: focal ratio, f number, stop number, speed. · · Noun Definition 1 Synonyms · · · focal ratio · · Synonym 1 stop number · · Synonym 2 speed · · Synonym 3 Characters · · space U+0020 b latin small letter b U+0062 e latin small letter e U+0065 f latin small letter f U+0066 m latin small letter m U+006D n latin small letter n U+006E r latin small letter r U+0072 u latin small letter u U+0075