Two or more atoms joined together by a chemical bond are known as what?

A molecule is defined as two or more atoms that are chemically bonded together. This can include atoms of the same element, like O2 (oxygen gas), or different elements, creating compounds, such as H2O (water). The focus here is on the bond between the atoms, which can be covalent, ionic, or metallic.

While the term "compound" also refers to a substance made up of two or more different elements, it specifically denotes a molecule that contains at least two different types of atoms. An element refers to a pure substance made up of only one type of atom, and an ionic bond describes a type of chemical bond formed through the transfer of electrons, which is just one of the many ways in which atoms can be combined to form molecules. Thus, the term that best fits the definition provided in the question is indeed a molecule.