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

Researchers observed similar results in both colorectal and breast cancer cells, suggesting that the relationship between tetraploid cell size and tumor aggressiveness may extend across different cancers.

From Science Daily ● Oct. 15, 2026

"The presence of even a small fraction of these tetraploid cells can promote the recruitment of extra non-cancerous cells that support further tumor progression," Sweet said.

From Science Daily ● Oct. 15, 2026

"They really do go straight to surgery only for the earliest stage tumors, which makes me think this was a very early stage tumor, and has a quite good prognosis."

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

He peered inside Henrietta, dilated her cervix, and prepared to treat her tumor.

From "The Immortal Life of Henrietta Lacks" by Rebecca Skloot

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

From Science Daily ● Oct. 15, 2026

The drug didn’t prove as effective in a wider population of breast-cancer patients whose tumors weren’t explicitly driven by the ESR1 mutation, a failure that led to a 53% stock selloff for Arvinas.

From The Wall Street Journal ● Oct. 15, 2026

The task force recommended against prostate-specific antigen tests in 2012—on the theory that it could turn up false positives and that slow-growing tumors are unlikely to kill patients.

From The Wall Street Journal ● Oct. 14, 2026

"They really do go straight to surgery only for the earliest stage tumors, which makes me think this was a very early stage tumor, and has a quite good prognosis."

From Barron's ● Oct. 14, 2026

Stories such as these spread through the camp and grew in our minds like tumors.

From "Farewell to Manzanar" by Jeanne Houston

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Related Words

• Cancer
• carcinoma
• cyst
• lump
• swelling

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