A pure substance that contains two or more elements is called a compound.

Here are some examples:

* Water (H₂O): Composed of hydrogen and oxygen.

* Carbon dioxide (CO₂): Composed of carbon and oxygen.

* Sodium chloride (NaCl): Composed of sodium and chlorine.

* Sugar (C₁₂H₂₂O₁₁): Composed of carbon, hydrogen, and oxygen.

The key characteristic of a compound is that its elements are chemically combined in a fixed ratio. This means that the compound always has the same proportions of each element, regardless of its source.