Excrete means to discharge from the body as waste, which is an essential process for all life forms. The term “excretion” can also be used to describe the process of excreting but it can also be used to describe the substance that is excreted. For example, when feces (poop) are excreted from the intestines, feces can be referred to as a type of excretion. The kidneys, lungs, and skin, play the main role in excreting substances from the bodies of animals. In this way, animals have special excretory organs. As other examples, the skin excretes wasteful products via sweating and urine is excreted from the urinary bladder. Excretions are usually, but not always, the products of metabolism. Metabolism refers to the chemical actions in cells that release energy from nutrients or use energy to create other substances. The process of excreting means that something is being separated from the blood and sent out of the body. In contrast to animals, single-celled organisms excrete substances from the surface of the cell.
It is important not to confusion an excretion with a secretion. In a secretion, unlike an excretion, the substance that is released has a function to perform after it is released from the body. An example of a secretion is a tear, which is released from the lacrimal apparatus and has specific functions (e.g., cleaning and lubricating the eye). By contrast, once urine (an excretion) leaves the body, it has no specific function. Excrete comes from the Latin word "excerene," meaning "to separate."