Some quantities are called fundamental because they are independent and cannot be defined in terms of other quantities. They are the building blocks of all other physical quantities.

Here's why this is important:

* Foundation for Measurement: Fundamental quantities provide a basis for defining and measuring all other physical quantities. For example, we can define velocity as the change in displacement over time, where both displacement and time are fundamental quantities.

* Consistency and Universality: By defining a set of fundamental quantities, we ensure that everyone uses the same units and measures the same things in the same way. This is essential for scientific communication and reproducibility of results.

* Simplicity and Clarity: Reducing the complexity of describing the world to a small set of fundamental quantities makes it easier to understand and work with.

Here are some examples of fundamental quantities and their corresponding units:

* Length: meter (m)

* Time: second (s)

* Mass: kilogram (kg)

* Temperature: Kelvin (K)

* Amount of Substance: mole (mol)

* Electric Current: ampere (A)

* Luminous Intensity: candela (cd)

It's important to note that the choice of which quantities are considered fundamental is a matter of convention and can change over time. For example, in the past, electric current was defined in terms of the force between two wires carrying electric current, but now it is considered a fundamental quantity.