Sun (noun)

1. The star that is the central body of the solar system, around which the planets revolve and from which they receive light and heat.
2. The light and heat radiated by the sun.
3. A self-luminous celestial body.

Origin:

Old english sunne; akin to old high german sunna sun, latin sol, greek helios.

Examples:

1. The sun rises in the east and sets in the west.
2. We put on sunscreen to protect ourselves from the sun.
3. The sun is the closest star to Earth.
4. The sun is a medium-sized star.
5. The sun is a major source of energy for life on Earth.