In physics, what do we call a quantity that has both magnitude and direction?

In physics, a quantity that has both magnitude and direction is defined as a vector. Vectors are crucial in various fields of physics because they not only tell you how much (the magnitude) but also in which direction that quantity is acting. For example, if you think about velocity, it is not enough to know that a car is moving at 60 kilometers per hour; you also need to know the direction it's traveling (e.g., north, south, east, or west) to fully understand its motion.

In contrast, scalars, which do not have a direction, are quantities that are described only by magnitude. Common examples of scalars include temperature and mass, where knowing the amount alone suffices without needing to specify a direction. Amplitude usually refers to the maximum extent of a vibration or oscillation and is not relevant to directional characteristics. Pressure is defined as force per unit area and, while it is a critical physical concept, it also fits within the scalar category since it does not involve direction.

Understanding the distinction between vectors and scalars is fundamental in physics, particularly when analyzing forces, motion, and other vector-dependent phenomena.