Luminosity is the quality of something that gives off light or shines with reflected light. The most noticeable quality of a large, sparkly diamond is its luminosity.

You might describe a bright and lively oil painting in terms of its luminosity, or marvel at the luminosity of a brilliant sunset. Astronomers use the word luminosity to talk about a specific property of physics, the energy given of by an astronomical object in a certain amount of time. There's a direct correlation between this amount of energy and the object's brightness. The Latin root is lumen, meaning "light."

Definitions of luminosity
  1. noun
    the quality of being luminous; emitting or reflecting light
    “its luminosity is measured relative to that of our sun”
    synonyms: brightness, brightness level, light, luminance, luminousness
    see moresee less
    illuminance, illumination
    the luminous flux incident on a unit area
    light from heat
    glow, luminescence
    light from nonthermal sources
    type of:
    physical property
    any property used to characterize matter and energy and their interactions
Word Family

Test prep from the experts

Boost your test score with programs developed by’s experts.

  • Proven methods: Learn faster, remember longer with our scientific approach.
  • Personalized plan: We customize your experience to maximize your learning.
  • Strategic studying: Focus on the words that are most crucial for success.


  • Number of words: 500+
  • Duration: 8 weeks or less
  • Time: 1 hour / week


  • Number of words: 500+
  • Duration: 10 weeks or less
  • Time: 1 hour / week


  • Number of words: 700+
  • Duration: 10 weeks
  • Time: 1 hour / week