What do you call a combination of two or more pure substances?

A combination of two or more pure substances is referred to as a mixture. Mixtures can consist of different substances that retain their individual properties and can be separated by physical means. For example, when sand and salt are combined, both the sand and salt maintain their distinct characteristics and can be filtered apart.

There are two main types of mixtures: homogeneous mixtures, where the components are evenly distributed (like saltwater), and heterogeneous mixtures, where the components are not uniformly distributed (like a salad). The term "mixture" encompasses both of these categories, making it the broad term for any physical combination of substances, as opposed to a single compound, which results from a chemical reaction between elements that cannot be separated by physical means.

Other terms like solution and homogeneous mixture refer to specific types of mixtures but do not cover all possible combinations of pure substances, while a compound indicates a specific chemical combination of elements that results in a substance with different properties from those of its constituent elements.