Any material made up of distinct elements, compounds, or both, not chemically combined with each other represents

The definition provided in the question accurately describes a mixture. A mixture consists of two or more substances—whether elements, compounds, or both—that are physically combined but not chemically bonded. This distinguishes a mixture from a compound, where the constituents undergo a chemical reaction to form a substance with new properties.

For example, if sand and salt are mixed together, each retains its individual properties and can be separated through physical means, such as filtration or evaporation. In contrast, a compound, like water, is formed when hydrogen and oxygen chemically combine in a specific ratio, resulting in new characteristics that differ from those of the individual gases.

The terminology in the other choices highlights specific concepts that do not align with the description in the question. An atomic structure pertains to the arrangement of atoms within a single element or compound, and a molecule refers to a group of atoms bonded together, often representing a single chemical species. Thus, while these concepts are related to the study of materials, they do not accurately fit the definition of distinct, non-chemically combined elements or compounds that characterize a mixture.