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

Abnormal chromosome numbers have long been linked to dangerous tumor behavior, but the new research indicates that cell size may offer additional clues about a cancer's potential to grow and spread.

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

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

Research into HPV eventually uncovered how Henrietta’s cancer started: HPV inserted its DNA into the long arm of her eleventh chromosome and essentially turned off her p 5 3 tumor suppressor gene.

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

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

Despite this decline, the tumors continued expanding rapidly and reached substantial sizes.

From Science Daily ● Oct. 15, 2026

Although painstaking, this work is helping scientists piece together why certain tumors become much more dangerous than others.

From Science Daily ● Oct. 15, 2026

The discoveries emerged from years of painstaking laboratory work, including the careful examination of tumors grown in mice.

From Science Daily ● Oct. 15, 2026

Its long body was covered in disgusting sores and tumors.

From "Beauty Queens" by Libba Bray

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Related Words

• Cancer
• carcinoma
• cyst
• lump
• swelling

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