Units and Standards of Measurement

A physical quantity is any number that describes a physical phenomenon quantitatively. For instance, length is a physical quantity that describes the distance between two points.

The measurements of physical quantities are expressed in terms of units. The mass of your body can be expressed in kilograms and your height in terms of meters.

Physical quantities expressed without standard units are difficult to understand. For example, if the height of the Eiffel Tower is reported to be 300, without providing units the context of the number is unclear. This means the Eiffel tower could be relatively tall, or very short.

In order to measure and report the various properties of matter accurately, a common system of measurement has been developed known as the International System of Units or the SI units.

The SI system recommends using seven base quantities and their units, which form the International System of Quantities.