What are Units and It’s type?

## What is Unit?

Unit is the quantity of a constant magnitude which is used to measure the magnitudes of other quantities of the same nature.
For the measurement of a physical quantity a definite magnitude of quantity is taken as standard and the name given to this standard is called unit.

## Properties of Unit

(a) The unit should be well-defined.
(b) The unit should be of some suitable size.
(c) The unit should be easily reproducible.
(d) The unit should not change with time.
(e) The unit should not change with physical conditions like pressure, temperature, etc.
(f) Unit should be of proper size.

## Types of Unit

(a) Fundamental Unit
(b) Derived Units

Fundamental Unit: The units for the fundamental or base quantities are called fundamental or base units. For e.g. kg for mass, seconds for time etc.
Derived Units: The units of all other physical quantities can be expressed as combinations of the base units. Such units obtained for the derived quantities are called derived units. For e.g. Velocity is a derived quantity, i.e.
derived from other fundamental quantities and its units $m s^{-1}$ are derived units.