Elemental composition refers to the types and amounts of elements that make up a substance. Every material, whether it's a rock, a plant, or a metal, is composed of different elements, which are the basic building blocks of matter. For example, water is made up of two hydrogen atoms and one oxygen atom, giving it the chemical formula H2O. Understanding elemental composition is crucial in various fields, including chemistry, geology, and biology. It helps scientists analyze materials, identify their properties, and understand their behavior. For instance, knowing the elemental composition of soil can inform agricultural practices and environmental studies.