kidney

American  

[kid-nee] / ˈkɪd ni /

noun

kidneys plural

1. Anatomy. either of a pair of bean-shaped organs in the back part of the abdominal cavity that form and excrete urine, regulate fluid and electrolyte balance, and act as endocrine glands.

2. Zoology. a corresponding organ in other vertebrate animals or an organ of like function in invertebrates.

3. the meat of an animal's kidney used as food.

4. constitution or temperament.

   He was a quiet child, of a different kidney from his boisterous brothers.

5. kind, sort, or class.

   He is only at ease with men of his own kidney.

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kidney British  

/ ˈkɪdnɪ /

noun

1. either of two bean-shaped organs at the back of the abdominal cavity in man, one on each side of the spinal column. They maintain water and electrolyte balance and filter waste products from the blood, which are excreted as urine

2. the corresponding organ in other animals

3. the kidneys of certain animals used as food

4. class, type, or disposition (esp in the phrases of the same or a different kidney )

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kidney Scientific  

/ kĭd′nē /

1. Either of a pair of organs that are located in the rear of the abdominal cavity in vertebrates. The kidneys regulate fluid balance in the body and filter out wastes from the blood in the form of urine. The functional unit of the kidney is the nephron. Wastes filtered from the blood by the nephrons drain into the ureters, muscular tubes that connect each kidney to the bladder.

2. See also nephron

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Other Word Forms

• kidneylike
  adjective

Etymology

Origin of kidney

1275–1325; Middle English kidenei, kidenere (singular), kideneres, kideneren (plural); origin uncertain; perhaps a compound based either on nere (singular), neres (plural) kidney ( Old English *nēore; compare Old High German nioro, Old Norse nȳra ); or ei (singular), eiren (plural) egg ¹, Old English ǣg (singular), ǣgru (plural) (by association with the organ's shape); for the first element compare dial. kid pod (akin to cod ² )

Explanation

Most people are born with two kidneys, internal organs with the job of filtering waste and excreting urine. All vertebrates — animals with spines — have kidneys. Human kidneys are shaped like large beans, and this is where the "kidney bean," a common red-colored bean, gets its name. The organs called kidneys are vital to life, as they filter bad stuff from your blood, help your body get rid of waste, regulate your blood pressure, and even produce hormones. The word kidney is probably a compound of the Old English cwið, "womb," and ey, "egg," describing the organ's shape.

Example Sentences

One surgeon revealed recently that he had to cancel a kidney transplant because he could not check the patient's history quickly enough.

From BBC • Jun. 1, 2026

This points to methionine as a possible tool for infectious diseases and inflammatory conditions, especially in people with kidney disease, kidney failure, or those undergoing dialysis.

From Science Daily • Jun. 1, 2026

The parents of a 3-year-old girl who experienced acute kidney failure after eating contaminated beef at The Kebab Shop in Costa Mesa also filed a lawsuit against the restaurant chain and Olympia Foods.

From Los Angeles Times • May 31, 2026

Days later, he ended up in an emergency room, where medical testing later confirmed an E. coli infection that resulted in a life-threatening kidney complication, according to his attorney.

From Los Angeles Times • May 31, 2026

But when Daisy left him the old man did not come anymore and he had to content himself with purges and kidney pills advertised in the newspapers.

From "The Heart is a Lonely Hunter" by Carson McCullers

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