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  

/ ˈəʊzəʊn, əʊˈzəʊn /

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; see 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

See Examples For:

ozone

Heatwaves and wildfires combined with human-caused emissions this year combined to expose one third of the world's population to extremely high levels of ozone pollution, a European Union report said on Wednesday.

From Barron's ● Sep. 30, 2026

Another 22 percent was exposed to "very poor" ozone.

From Barron's ● Sep. 30, 2026

Despite progress in cutting the most harmful air pollutants in recent decades, ozone has proved more difficult to tackle as climate change fuels the conditions that favour its formation.

From Barron's ● Sep. 30, 2026

The researchers say exposure can be reduced by choosing unscented products, improving ventilation with exhaust fans or open windows, and avoiding devices that generate ozone while scented cleaning products are being used.

From Science Daily ● Sep. 26, 2026

As I got nearer to him, the air crackled and smelled of ozone.

From "The Lightning Thief" by Rick Riordan

Related Words

• atmosphere
• breeze
• wind