Definition

1. Noun:
   • (Astronomy) An immense cloud of gas (mainly hydrogen) and dust in interstellar space. A nebula is a vast, diffuse cloud in space, often the birthplace of stars or the remnants of a star's death.
   • (Pathology) A faint cloudy spot on the cornea. In medicine, a nebula is a slight opacity or scar on the cornea of the eye, causing a minor cloudiness in vision.
   • (Pharmacy) A medicinal liquid preparation intended for use in an atomizer. This is a specialized term for a fine spray or mist used for inhalation.
   • Cloudiness of the urine. An archaic or highly specialized medical term for a cloudy appearance in urine.

Usage Examples

• Astronomy:
  • The Orion Nebula is a stellar nursery where new stars are forming.
  • Through the telescope, we observed a beautiful glowing nebula.
• Pathology:
  • The ophthalmologist noted a small nebula on the patient's cornea from an old injury.
• Pharmacy:
  • The doctor prescribed a saline nebula for the patient's respiratory therapy.

Advanced Usage

• "Planetary nebula": A specific type of nebula formed from the outer layers of a dying, low-mass star, often appearing as a glowing shell of gas.
  • The Ring Nebula is a famous example of a planetary nebula.
• "Diffuse nebula": A broad category of nebulae that are extended and lack well-defined boundaries, often illuminated by nearby stars.
  • Emission nebulae and reflection nebulae are types of diffuse nebulae.

Variants and Related Words

• Nebulae (n): The standard plural form of nebula.
  • The Hubble Space Telescope has captured images of countless nebulae.
• Nebular (adj): Relating to or resembling a nebula.
  • The nebular hypothesis is a theory for the formation of the solar system.
• Nebulizer (n): A device that converts a liquid medicine into a fine mist (a nebula) for inhalation. This is the common modern term derived from the pharmaceutical sense.
  • She uses a nebulizer to administer her asthma medication.

Synonyms

• Astronomy: Cloud, interstellar cloud, galactic cloud.
• Pathology: Corneal opacity, corneal scar, leucoma (a more dense opacity).

Notes on Meaning

• The primary and most common modern usage is the astronomical meaning. When people say "nebula," they are almost always referring to the cosmic clouds.
• The medical (pathology) meaning is technical and less common in everyday language.
• The pharmaceutical meaning is largely historical or highly specialized; the device is now almost exclusively called a nebulizer.
• The urine cloudiness meaning is obsolete.

Noun

1. (pathology) a faint cloudy spot on the cornea
2. an immense cloud of gas (mainly hydrogen) and dust in interstellar space
3. cloudiness of the urine
4. a medicinal liquid preparation intended for use in an atomizer