What does smog mean?
Smog is a blend of smoke and fog, used today especially for the polluted haze that hangs over cities and industrial areas. It contains fine particles and can also include gases such as nitrogen oxides and ozone, so breathing smog may irritate the eyes and lungs and worsen asthma or other respiratory conditions. The word commonly appears in phrases such as “urban smog,” “thick smog,” and “smog alert,” and it is often discussed in relation to traffic emissions, industrial pollution, and weather conditions that trap pollutants near the ground. Although the combination of smoke and fog has long existed, the modern expression developed during the early twentieth century, when coal-burning cities experienced increasingly serious forms of polluted haze. Smog remains a familiar word because air quality directly affects visibility, public health, and daily life.
A mixture of smoke and fog or other haze, especially polluted air that obscures visibility and may harm health.
"A blanket of smog covered the city at sunrise."
The word often refers to urban or industrial air pollution and can imply health risks as well as reduced visibility.
To cover an area with smog or fill the air with smog.
"Heavy traffic smogged the valley throughout the afternoon."
This verb form is much less common than the noun and is mainly used in descriptive or literary contexts.
The plural is used when referring to separate smog events, distinct layers of smog, or examples of smog in different places.
"The smogs that settled over the region lasted for several days."
Smog is literally smoke and fog combined—and in cities today, it often signals a dangerous blend of traffic fumes, industrial pollution, and trapped moisture.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does smog come from?
“Smog” is a blend of the English words “smoke” and “fog,” formed in the early twentieth century. Its development is associated with growing awareness of polluted urban air, especially haze produced by industrial coal smoke and moisture. The blend later became widely used for severe atmospheric pollution, while the related forms “smoggy” and “smogging” developed from the same modern word.
Related word forms
How smog is actually used
Smog is common in environmental, health, and weather reporting. In everyday use, it usually suggests polluted, unhealthy air rather than ordinary fog.
Easily confused with smog
Smoke generally refers to visible gases and particles released by burning, whereas smog specifically combines smoke with fog or other forms of haze.
Fog is a cloud of tiny water droplets near the ground, while smog is haze or pollution containing smoke or other harmful particles.