Soundness refers to the quality of an argument or reasoning that is both valid and has true premises. In logic, a sound argument guarantees that if the premises are true, the conclusion must also be true. This means that soundness is a stronger condition than mere validity, which only requires that the conclusion logically follows from the premises. In practical terms, soundness is important in fields like mathematics and philosophy, where clear reasoning is essential. For example, a sound argument about the properties of triangles would not only follow logical rules but also rely on true statements about geometry.