What is a substance made up of one or more elements bonded together?

A substance made up of one or more elements bonded together is known as a compound or a molecule, depending on the context. Compounds consist of two or more different elements that are chemically combined in fixed ratiOS, such as water (H₂O), which is made of hydrogen and oxygen. Molecules can also refer to the smallest units of compounds or elements that retain their chemical properties. For example, O₂ is a molecule consisting of two oxygen atoms bonded together.