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

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)

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

In June 2022, Burrell was diagnosed with an incurable, aggressive Grade 4 brain tumor, and was told she had a year to a year and a half to live.

From Los Angeles Times ● Jul. 14, 2026

After multiple trips to various physicians and a CT scan, doctors found an about 2-inch-diameter brain tumor in the right side of her brain.

From Los Angeles Times ● Jul. 14, 2026

In mouse models of aggressive prostate cancer, the targeted particles produced several complete tumor remissions, offering encouraging evidence that the approach could eventually advance to human clinical trials.

From Science Daily ● Jul. 9, 2026

The study showed that cDC2 cells can also activate T cells and help prevent tumor growth.

From Science Daily ● Jul. 9, 2026

"It isn't very serious. I have this tiny little tumor on the brain."

From "The Catcher in the Rye" by J. D. Salinger

Many of these geckos developed aggressive tumors that frequently spread to other parts of the body.

From Science Daily ● Jul. 15, 2026

Because these tumors often metastasize, the reptiles provide scientists with a rare chance to observe how cancer begins, evolves, and spreads under natural conditions.

From Science Daily ● Jul. 15, 2026

Its presence attracted T cells, B cells, and neutrophils into tumors.

From Science Daily ● Jul. 10, 2026

She competed with other researchers for access to scarce tissue samples from human tumors and led a team analyzing them for clues.

From The Wall Street Journal ● Jul. 10, 2026

I know five kinds of fever, and four humors, Bloodletting, and the way to feel for tumors.

From "Good Masters! Sweet Ladies!: Voices from a Medieval Village" by Laura Amy Schlitz

Related Words

• Cancer
• carcinoma
• cyst
• lump
• swelling