Main Entry: kid·ney

Pronunciation: \ˈkid-nē\

Function: noun

Inflected Form(s): plural kidneys

1 : one of a pair of vertebrate organs situated in the body cavity near the spinal column that excrete waste products of metabolism, in humans are bean-shaped organs about 4¹⁄₂ inches (11¹⁄₂ centimeters) long lying behind the peritoneum in a mass of fatty tissue, and consist chiefly of nephrons by which urine is secreted, collected, and discharged into the pelvis of the kidney whence it is conveyed by the ureter to the bladder—compare mesonephros, metanephros, pronephros

[kidney illustration]

2 : any of various excretory organs of invertebrate animals