Which of the following describes a physical quantity that only expresses magnitude?

A physical quantity that only expresses magnitude is known as a scalar. Scalars are quantities that are described by a single numerical value along with its unit, such as mass, temperature, and speed. They do not have a direction associated with them, distinguishing them from vectors, which are quantities that include both magnitude and direction, such as velocity and force.

In this context, while "magnitude" refers to the size or amount of a quantity, it does not encapsulate the concept of a quantity that only expresses magnitude; it’s more of a component of a scalar representation. Force, on the other hand, is a vector quantity, as it has both magnitude and direction. Therefore, the most accurate description for a quantity that solely expresses magnitude is a scalar.