Scalars

A physical quantity that can be completely described by its magnitude alone is called a scalar. Stating a scalar quantity means giving a number together with the appropriate unit; the two together give the complete physical meaning of the quantity, with no reference to any direction.

For example, when we say a metal rod has a length of 2 m, the number 2 tells us the rod is two times as long as the standard unit (the metre); the number (2) is called the magnitude and 'metre' is the unit. Together, magnitude and unit give a complete description of the rod's length — no direction is involved, so length is a scalar quantity. …