It is a derived unit of luminous flux. Luminous flux is defined as the assessment of the perceived power of light. Luminous flux is being measured in Lumen.

One lumen is defined as the luminous flux of light generated by the source that emits one candela of luminous intensity over a solid angle of one Steradian.

Luminous intensity is measurement of wavelength emitted by the power source in a particular direction per unit solid angle.