kidney

American  

[kid-nee] / ˈkɪd ni /

noun

plural

kidneys

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

Grams pointed out that cystatin C testing was first recommended in 2012 by the international organization Kidney Disease -- Improving Global Outcomes.

From Science Daily • Jan. 21, 2026

The research was funded by National Institutes of Health grant R01DK100446 and by the National Kidney Foundation.

From Science Daily • Jan. 21, 2026

The findings were unveiled at the American Society of Nephrology Kidney Week 2025 and released at the same time in The New England Journal of Medicine.

From Science Daily • Jan. 10, 2026

According to the National Kidney Registry, approximately 90,000 people in the U.S. are currently in need of a kidney transplant, while roughly 6,000 people donate kidneys each year.

From Los Angeles Times • Oct. 31, 2025

She also left money to the North Shore Animal League and to the National Kidney Foundation.

From "Genuine Fraud" by E. Lockhart

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