tumor

American  

[too-mer, tyoo-] / ˈtu mər, ˈtju- /

especially British, tumour

noun

• tumors
  plural

1. a swollen part; swelling; protuberance.

2. an uncontrolled, abnormal, circumscribed growth of cells in any animal or plant tissue; neoplasm.

3. Archaic.

   1. inflated pride; haughtiness.

   2. pompous language; bombast.

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tumor Scientific  

/ to̅o̅′mər /

1. See neoplasm See Note at cancer

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tumor Cultural  

1. An abnormal mass of new tissue growth that serves no function in the body. Tumors are usually classified as benign or malignant and are often caused by cancer.

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Other Word Forms

Derived Forms

• antitumor
  adjective
• antitumoral
  adjective
• nontumorous
  adjective
• tumoral
  adjective
• tumorlike
  adjective
• tumorous
  adjective

Inflected Forms

Nouns

• tumors
  plural

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Etymology

Origin of tumor

First recorded in 1535–45; from Latin: “a swelling, swollen state,” equivalent to tum(ēre) “to swell” + -or noun suffix ( see -or ¹)

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Explanation

A tumor is a growth — a mass of tissue — that has no function. Tumors can be harmless (benign) or harmful (malignant), but they are never any fun. When a bunch of cells form a new growth in or on an animal, and those cells have no purpose, the result is a tumor. The word tumor comes directly from Latin word for “swelling.” Tumors can be big or small, harmless or harmful. Benign tumors are not a cause for concern, but a malignant tumor is serious and could be cancerous. A doctor must test a tumor to see which kind it is.

Example Sentences

See Examples For:

tumor tumors

Graduate student Megan Sweet, who studies biological sciences at Virginia Tech, spends much of her time preparing extremely thin slices of tumor tissue.

From Science Daily ● Oct. 15, 2026

Working inside a refrigerated metal chamber, she carefully adjusts a mounted tumor, roughly the size of a pinkie fingernail, toward a sharp cutting blade.

From Science Daily ● Oct. 15, 2026

Pope Leo XIV had a cancerous tumor surgically removed from his right lung on Tuesday in a 90-minute operation described as "successful" by the Vatican.

From Barron's ● Oct. 14, 2026

She told AFP that "is a good thing" because it means the tumor is from lung cancer instead of generating from the spread of another cancer.

From Barron's ● Oct. 14, 2026

“Your cancer is not going away, Hazel. But we’ve seen people live with your level of tumor penetration for a long time.”

From "The Fault in Our Stars" by John Green

Existing therapies based on engineered T cells have achieved their greatest successes against certain blood cancers, but treating solid tumors has proven more difficult.

From Science Daily ● Oct. 16, 2026

The former University of Virginia standout was reportedly diagnosed with the Grade 4 cancer last year and briefly went into remission, but the tumors returned in July, according to Houston news site Chron.

From Los Angeles Times ● Oct. 16, 2026

This engineered receptor allows immune cells to identify a particular molecular marker on the surface of cancer cells, helping direct their activity toward tumors.

From Science Daily ● Oct. 16, 2026

As tumors grew in mice, the proportion of tetraploid cells actually decreased.

From Science Daily ● Oct. 15, 2026

In human populations exposed to urethane or related chemicals there is a possibility that tumors will develop in infants through prenatal exposure, as Dr. Hueper has warned.

From "Silent Spring" by Rachel Carson

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Related Words

• Cancer
• carcinoma
• cyst
• lump
• swelling

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