ozone

American  

[oh-zohn, oh-zohn] / ˈoʊ zoʊn, oʊˈzoʊn /

noun

1. a form of oxygen, O 3 , with a peculiar odor suggesting that of weak chlorine, produced when an electric spark or ultraviolet light is passed through air or oxygen. It is found in the atmosphere in minute quantities, especially after a thunderstorm, is a powerful oxidizing agent, and is thus biologically corrosive. In the upper atmosphere, it absorbs ultraviolet rays, thereby preventing them from reaching the surface of the earth. It is used for bleaching, sterilizing water, etc.

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ozone British  

/ əʊˈzəʊn, əʊˈzɒnɪk, ˈəʊzəʊn /

noun

1. Technical name: trioxygen.  a colourless gas with a chlorine-like odour, formed by an electric discharge in oxygen: a strong oxidizing agent, used in bleaching, sterilizing water, purifying air, etc. Formula: O 3 ; density: 2.14 kg/m³; melting pt: –192°C; boiling pt: –110.51°C

2. informal clean bracing air, as found at the seaside

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ozone Scientific  

/ ō′zōn′ /

1. An unstable, poisonous allotrope of oxygen having the chemical formula O ₃. Ozone forms in the atmosphere through the process of photolysis, when ultraviolet radiation from the Sun strikes oxygen molecules (O ₂), causing them to split apart. When freed oxygen atoms bump into and join other O ₂ molecules, they form ozone. Although ozone is broken down naturally in the atmosphere through chemical reactions with other atmospheric gases (such as nitrogen, hydrogen, and chlorine), in an unpolluted atmosphere the formation and breakdown of ozone is generally balanced, and the total concentration of ozone is relatively constant. The formation and destruction rates of ozone vary with altitude in the atmosphere, and with latitude. Most ozone forms in the 15 to 30 km (10 to 19 mi) altitude range and in latitudes closest to the equator where sunshine strikes the Earth the most. The ozone is then transported northward and southward by wind and is generally most concentrated in areas above the Canadian Arctic and Siberia and above Antarctica. Ozone is used commercially in water purification, in air conditioning, and as a bleach.

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Closer Look

Ozone is both beneficial for and threatening to all of Earth's organisms, including human beings, depending on how high in the atmosphere it is found. Ozone is naturally produced in the stratospheric portion of Earth's atmosphere (in the ozone layer) by the action of high-energy ultraviolet radiation on molecular oxygen (O₂ ). By absorbing much of the Sun's ultraviolet radiation, the ozone layer serves as a sunscreen for organisms on Earth. In recent years the ozone has thinned or disappeared in parts of the ozone layer, creating an ozone hole that lets in dangerous amounts of ultraviolet radiation. Ozone holes are caused in part by the release into the atmosphere of industrial and commercial chemicals, in particular the chlorofluorocarbons (such as freon) used in aerosols, refrigerants, and certain cleaning solvents. Closer to Earth's surface, ozone is one of the so-called greenhouse gases that are produced by the burning of fossil fuels and cause the greenhouse effect. Ozone at ground level is also an air pollutant, contributing to respiratory diseases such as asthma.

Other Word Forms

• ozonic adjective

Etymology

Origin of ozone

< German Ozon < Greek ózōn, present participle of ózein to smell; ozo-

Explanation

Ozone is a colorless toxic gas formed from oxygen by an electrical discharge. It’s that stuff in the sky that comes between you and the sun. If there weren’t a hole in the ozone layer, you’d probably hear the word ozone much less often. Certainly, we should be thankful that the powerful ozone is up there protecting us from the sun’s rays, but you don’t want to encounter ozone closer to the ground — it’s toxic. It also has a very strong smell, which is how it got its name; a German chemist took the name from the Greek ozon, meaning "to smell."

Example Sentences

The Strait of Hormuz is a crucial shipping chokepoint for Persian Gulf energy exports, other chemicals like ozone, and fertilizer.

From Barron's • Apr. 4, 2026

And this will blow your mind: The cooking from L.A.’s fab new restaurant scene creates as much man-made ozone as our cars do — one-quarter of the total!

From Los Angeles Times • Mar. 26, 2026

The process follows a special ozone treatment for sterilisation, bleaching and deodorisation.

From Barron's • Mar. 25, 2026

He draws parallels to chlorofluorocarbons pollutants released from refrigerators that bore a hole in the ozone layer last century, and were eventually banned.

From BBC • Feb. 19, 2026

This late, its scent is distinct, a sharp blend of ozone and pine.

From "Beasts of Prey" by Ayana Gray

Related Words

• atmosphere
• breeze
• wind