We'd like to use analytics cookies to understand which symbols people look up, so we know what to research next. They are not used for advertising and we set none of them unless you say yes. What we store.
The two letters cd, the SI unit symbol for the candela.
cd is the SI symbol for the candela, the base unit of luminous intensity — the only base unit whose definition is weighted to the sensitivity of the human eye.
Denotes the candela, the SI base unit of luminous intensity.
Contexts: Mathematics
Measures perceived brightness rather than raw radiant power: its definition fixes the luminous efficacy of radiation at 540 × 10¹² hertz, close to the eye's peak daylight sensitivity, so the same wattage of red or blue light yields fewer candelas.
Contexts: Mathematics
Two lower-case Latin letters side by side: a c forming an open curve, followed by a d with a round bowl on the left and a vertical ascender on its right.
Luminous intensity in one direction, and total light output in every direction.