nebula

American  

[neb-yuh-luh] / ˈnɛb yə lə /

noun

plural

nebulae, nebulas

1. Astronomy.

   1. Also called diffuse nebula.  a cloud of interstellar gas and dust.

   2. (formerly) any celestial object that appears nebulous, hazy, or fuzzy, and extended in a telescope view.

2. Pathology.

   1. a faint opacity in the cornea.

   2. cloudiness in the urine.

3. any liquid medication prepared for use as a spray.

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nebula British  

/ ˈnɛbjʊlə /

noun

1. astronomy a diffuse cloud of particles and gases (mainly hydrogen) that is visible either as a hazy patch of light (either an emission or a reflection nebula ) or an irregular dark region against a brighter background ( dark nebula ) Compare planetary nebula

2. pathol

   1. opacity of the cornea

   2. cloudiness of the urine

3. any substance for use in an atomizer spray

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nebula Scientific  

/ nĕb′yə-lə /

plural

nebulae

1. A visible, thinly spread cloud of interstellar gas and dust. Some nebulae are the remnants of a supernova explosion, others are gravity-induced condensations of the gases in the interstellar medium which in certain cases may become a site for the formation of new stars. The term was formerly used of any hazy, seemingly cloudlike object, including what are now recognized as other galaxies beyond the Milky Way; it is restricted now to actual clouds of gas and dust within our own galaxy.

2. ◆ Nebulae are generally classified as bright or dark. Among the bright nebulae are cold clouds that reflect light from nearby stars (reflection nebulae) and hot, ionized clouds that glow with their own light (emission nebulae). Dark nebulae—cold clouds that absorb the passing light from background stars—are called absorption nebulae.

3. See more at star

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nebula Cultural  

1. plur. nebulae In astronomy, a hazy patch of light visible in the sky. Some nebulae are clouds of gas within the Milky Way; others are distant galaxies.

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Other Word Forms

• nebular adjective
• nonnebular adjective
• prenebular adjective

Etymology

Origin of nebula

First recorded in 1655–65; from Latin: “cloud, mist, vapor”; akin to German Nebel “fog, haze,” Greek nephélē “cloud,” Sanskrit nábha- “cloud, vapor”

Explanation

A nebula is a massive cloud of gas and dust in outer space. A nebula is sometimes the birthplace of stars, such as the Orion Nebula where new stars — a youthful million years old — are still forming. Another example of a nebula is the Crab Nebula — the glowing result of a supernova, noted by Chinese astronomers in 1054 CE. It spans about 10 light-years in length. In biology, a nebula may be a cloudy formation in the eye, or a cloudiness of urine. It also refers to a medicinal preparation put in a nebulizer. When you are talking about more than one nebula (which is probably not that often for the average person), say nebulae.

Example Sentences

New images from NASA's James Webb Space Telescope are providing a clearer look at a mysterious and rarely studied nebula surrounding a dying star.

From Science Daily • Mar. 17, 2026

The collisions carve and sculpt the nebula, creating its intricate and textured appearance.

From Science Daily • Jan. 26, 2026

And perfectly in time for Halloween, they captured a spooky, red-glowing nebula that looks just like a bat signal shining across the universe!

From Space Scoop • Oct. 31, 2025

The Andromeda nebula, M31, was a prominent example.

From Salon • Feb. 14, 2025

And some worlds will look out onto a vast gaseous nebula, the remains of an ordinary star that once was and is no longer.

From "Cosmos" by Carl Sagan