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

Soot, one of the protagonists of Mott’s funny and affecting new book, also appeared in 2021’s “Hell of a Book.”

From Los Angeles Times • Aug. 1, 2025

Soot triggers the formation of contrails and 'contrail cirrus', which are line-shaped clouds produced by aircraft engine exhaust.

From Science Daily • Nov. 28, 2023

Soot looks black because it absorbs light in the visible part of the spectrum—that is, the kind of light we see.

From Scientific American • Jun. 16, 2023

Soot is also known as fine particulate matter because its fragments are so small — 2.5 microns in diameter or less.

From Salon • Jan. 13, 2023

Soot stains blackened both legs of his uncle's likeness.

From "A Game of Thrones" by George R.R. Martin

Related Words

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