What is the term for a homogeneous mixture of two or more substances?

The term for a homogeneous mixture of two or more substances is a solution. In chemistry, a solution is formed when a solute (the substance that is dissolved) is uniformly distributed within a solvent (the substance that does the dissolving), resulting in a mixture that has the same composition throughout. This uniformity distinguishes solutions from heterogeneous mixtures, where different components can be easily identified or separated.

In a solution, the interactions between the solute and solvent molecules lead to a stable, consistent mixture. Common examples of solutions include salt water, where salt (the solute) is dissolved in water (the solvent).

The other terms listed refer to different concepts. A concentration gradient describes the difference in concentration of a substance across a space, cohesion refers to the attraction between molecules of the same substance, and enzymes are biological catalysts that speed up chemical reactions. None of these terms describe a mixture like a solution.