essential element

An essential element is an element needed by a living organism so that it can grow, develop, and maintain its body structure normally. All organisms on Earth require carbon, hydrogen, nitrogen, and oxygen, which they take in the form of food, air, and water, and which make up most of their body tissues. In addition, most organisms also need calcium, chlorine, magnesium, phosphorus, potassium, sodium, and sulfur, which are termed major elements. Required in much smaller quantities are trace element. All of these additional essential elements – major and trace – have to be supplied by the organism's food.