Luminosity (noun)

1. The quality of being bright, shining, or glowing.
2. The rate at which energy is emitted by a celestial body, especially a star, as measured in units of power per unit of surface area.
3. The brightness of a source of light, as measured in candles, lumen, or other units.

Origin:

The word 'luminosity' comes from the latin word 'lumen' meaning 'light'.

Examples:

1. The room was filled with the luminosity of the sun, streaming in through the large windows.
2. The luminosity of the star is an important factor in determining its temperature and classification.
3. The luminosity of the lightbulb was measured in watts, determining its brightness and energy efficiency.
4. The object's luminosity changed over time, indicating that it may be a pulsating star.
5. The city was lit up with the luminosity of thousands of lights, creating a brilliant nighttime skyline.