focal ratio focal point • focal seizure · · · Info · Definitions · Synonyms · Characters · · focal ratio · · Text Common · · Latin · · Scripts 11 · · Length 4 · · 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 · · · f number · · Synonym 1 stop number · · Synonym 2 speed · · Synonym 3 Characters · · space U+0020 a latin small letter a U+0061 c latin small letter c U+0063 f latin small letter f U+0066 i latin small letter i U+0069 l latin small letter l U+006C o latin small letter o U+006F r latin small letter r U+0072 t latin small letter t U+0074