What meant by one candela? And Which base quantity is measured by this unit? (or) Define one candela (S.I standard for Luminous intensity)

What meant by one candela? And Which base quantity is measured by this

1.	What meant by one candela? And Which base quantity is measured by this unit? (or) Define one candela (S.I standard for Luminous intensity)
Answer» Solution :One candela is the luminous INTENSITY in a given DIRECTION, of a source that emits monochromatic radiation of FREQUENCY `5.4 xx 10^(14) Hz` and that has a radiant intensity of `(1)/(683)` watt/steradian in that direction.