Definitions for "Full sun"
plants that thrive in direct sunlight
The full sun condition is the amount of power density received at the surface of the earth at noon on a clear day - about 100 mW/cm2. Lower levels of sunlight are often expressed as 0.5 sun or 0.1 sun. A figure of 0.5 sun means that the power density of the sunlight is one-half of that of a full sun.
The amount of energy in sunlight striking the earth's surface at noon on a clear day (about 1,000 Watts per Square Meter).