luminosity

Everyday

1. (science) How much light something gives out; its brightness. tree →
2. (astronomy) The total amount of energy a star gives out each second, which is not the same as how bright it looks from Earth. tree →
3. (formal) A shining or glowing quality. tree →

In the lessons

In science lessons luminosity is used about stars, light bulbs and screens. A star with high luminosity is truly very bright, but it may look faint if it is very far away. In everyday life «brightness» is used for phone or TV screens. Phrases: high luminosity, low luminosity, the luminosity of a star.

Examples

• The Sun's luminosity keeps our planet warm. tree →
• Some stars have much greater luminosity than the Sun. tree →
• A distant star can have high luminosity but look dim. tree →
• The luminosity of the screen was turned down at night. tree →
• Glow-worms have a soft luminosity. tree →
• Scientists measure the luminosity of stars with special tools. tree →
• The painting had a strange luminosity, as if it glowed. tree →

Note

Mostly uncountable. Formal and scientific; in everyday talk say «brightness». Related: luminous (giving out light, glowing). Trap: in astronomy, luminosity (true power) differs from apparent brightness (how bright it looks from here).