A combination of two or more substances that are chemically combined is called a compound.

Here's why:

* Chemically combined: This means the substances have reacted with each other, forming new chemical bonds. The resulting compound has properties different from the original substances.

* Substances: These can be elements (like hydrogen and oxygen) or other compounds.

* Example: Water (H₂O) is a compound formed by the chemical combination of hydrogen and oxygen.

Let me know if you'd like to know more about compounds!