How is a quantity defined by its magnitude referred to?

A quantity defined by its magnitude is referred to as a scalar. Scalars are those physical quantities that can be described solely by a numerical value and a unit of measurement, without any consideration of direction. For example, temperature, mass, and speed are all scalars because they are characterized only by their size (magnitude) and do not have a directional component.

This understanding is essential in various fields such as physics and engineering, where differentiating between scalar and vector quantities can significantly impact the analysis and application of concepts. Vectors, in contrast, have both magnitude and direction, making them suitable for representing quantities like force or velocity. The term "parameter" often refers to a variable that defines a particular characteristic of a system, and a "constant" refers to a value that does not change under specified conditions. Therefore, these two terms do not adequately capture the concept of magnitude alone.