No, compounds are not made up of two or more substances. They are made up of two or more elements chemically combined in a fixed ratio.

Here's why:

* Substance: A pure form of matter with a definite and constant composition. Elements and compounds are substances.

* Element: A pure substance that cannot be broken down into simpler substances by chemical means. Examples: oxygen (O), carbon (C), hydrogen (H)

* Compound: A substance formed when two or more different elements chemically combine in a fixed ratio. Examples: water (H₂O), carbon dioxide (CO₂)

In summary: Compounds are made up of elements, not substances. The elements are chemically combined in a fixed ratio, making the compound a distinct substance with unique properties different from its constituent elements.