Water is called H₂O because of its chemical composition. Here's a breakdown:

* H: The "H" stands for hydrogen. Each water molecule contains two hydrogen atoms.

* 2: The subscript "2" indicates that there are two hydrogen atoms in the molecule.

* O: The "O" stands for oxygen. Each water molecule contains one oxygen atom.

Therefore, the chemical formula H₂O accurately reflects the fact that water is composed of two hydrogen atoms and one oxygen atom.