soot

American  

[soot, soot] / sʊt, sut /

noun

1. a black, carbonaceous substance produced during incomplete combustion of coal, wood, oil, etc., rising in fine particles and adhering to the sides of the chimney or pipe conveying the smoke: also conveyed in the atmosphere to other locations.

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verb (used with object)

1. to mark, cover, or treat with soot.

soot British  

/ sʊt /

noun

1. finely divided carbon deposited from flames during the incomplete combustion of organic substances such as coal

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verb

1. (tr) to cover with soot

soot Scientific  

/ st /

1. A black, powdery substance that consists mainly of carbon and is formed through the incomplete combustion of wood, coal, diesel oil, or other materials. Because it absorbs energy from sunlight rather than reflecting it, soot is believed to be a cause of global warming, especially when it settles on snow and ice, reducing their reflectivity. Soot particles in the air are a contributing factor in respiratory diseases.

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Other Word Forms

• sootless adjective
• sootlike adjective

Etymology

Origin of soot

before 900; Middle English; Old English sōt; cognate with Old Norse sōt

Explanation

The powdery black stuff that's sometimes created when fuel burns is called soot. A chimney sweep's job is to clean all the soot and ash from inside a chimney. Soot is mostly made of carbon, and it forms when matter burns incompletely. Engines, burning coal, and house fires are all sources of soot, and soot is a major contributor to air pollution around the world. It's dangerous for people to breathe too much soot into their lungs. Soot comes from a Germanic root that literally means "what settles."

Example Sentences

Home heating in the late 19th and early 20th centuries relied on wood- or coal-burning fireplaces or stoves that required constant tending of fires and ash and soot removal, and provided only uneven heat distribution.

From The Wall Street Journal • Apr. 9, 2026

Under this hypothesis, the blasts ignited widespread fires that filled the atmosphere with smoke, soot, and dust.

From Science Daily • Jan. 1, 2026

Abandoned for years, it is scarred by soot from a 2014 fire that gutted parts of the structure.

From BBC • Nov. 25, 2025

The Environmental Protection Agency in 2024 had strengthened limits on fine particulate matter, including soot, which can lead to health problems including strokes, heart attacks and asthma attacks.

From Barron's • Nov. 25, 2025

The few remaining barrels were being rolled to the open hatch to be hefted on deck by a handful of waiting men in their haphazard blanket and coal soot disguises.

From "Glitch" by Laura Martin

Related Words

• ash
• grit
• gunk
• residue
• sediment
• smoke