https://doi.org/10.1351/goldbook.C00787
SI base unit for @L03647@ (symbol: \(\text{cd}\)). The \(\text{candela}\) is the @L03647@, in a given direction, of a source that emits monochromatic radiation of frequency \(540\times 10^{12}\ \text{hertz}\) and that has a @R05045@ in that direction of (\(\frac{1}{683}\)) \(\mathrm{watt}\) per \(\mathrm{steradian}\).
Sources:
Green Book, 2nd ed., p. 70 [Terms] [Book]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 964 [Terms] [Paper]