* Fixed Composition: Water always consists of two hydrogen atoms and one oxygen atom, represented by the chemical formula H₂O. This fixed ratio of elements is a defining characteristic of compounds.

* Different Properties: Water has distinctly different properties compared to its constituent elements, hydrogen and oxygen. Hydrogen is a flammable gas, while oxygen is a colorless and odorless gas. Water is a liquid at room temperature, has a high boiling point, and is essential for life.

* Chemical Reaction: Water is formed by a chemical reaction between hydrogen and oxygen. This reaction involves the breaking and forming of chemical bonds, resulting in a new substance with distinct properties.

* Decomposition: Water can be broken down into its constituent elements (hydrogen and oxygen) through electrolysis, a process that requires energy to break the chemical bonds holding the compound together.

Therefore, due to its fixed composition, distinct properties, formation through a chemical reaction, and ability to be decomposed into its elements, water definitively fulfills the criteria of a compound.