Calcium is a chemical element with the symbol Ca and atomic number 20. It is a soft, silvery-white metal and an essential mineral for living organisms. In the human body, calcium helps build and maintain strong bones and teeth, supports muscle movement, aids nerve function, and plays an important role in blood clotting and heart function. It is commonly found in dairy products, leafy green vegetables, and fortified foods, while in nature it occurs in compounds such as limestone rather than in its pure form.