Daylight

Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and both of these reflected by Earth and terrestrial objects, like landforms and buildings. Sunlight scattered or reflected by astronomical objects is generally not considered daylight. Therefore, daylight excludes moonlight, despite it being reflected indirect sunlight.

Definition

Daylight is present at a particular location, to some degree, whenever the Sun is above the local horizon. This is true for slightly more than 50% of the Earth at any given time, since the Earth's atmosphere refracts some sunlight even when the Sun is below the horizon.
Outdoor illuminance varies from 120,000 lux for direct sunlight at noon, which may cause eye pain, to less than 5 lux for thick storm clouds with the Sun at the horizon, which may make shadows from distant street lights visible. It may be darker under unusual circumstances like a solar eclipse or very high levels of atmospheric particulates, which include smoke, dust, and volcanic ash.

For comparison, nighttime illuminance levels are:

Illuminance	Example
<1 lux	Moonlight, clear night sky
0.25 lux	A full Moon, clear night sky
0.01 lux	A quarter Moon, clear night sky
0.002 lux	Starlight and airglow, clear moonless night sky
0.0002 lux	Starlight, clear moonless night sky, excluding airglow
0.00014 lux	Venus at brightest, clear night sky
0.0001 lux	Starlight, overcast moonless night sky

For a table of approximate daylight intensity in the Solar System, see sunlight.