The International System of Units is used just for convenience and easy communication of these scientific units.
Explanation:
International unit system is the modern system of units used to measure quantities like length(m), speed (m/s), mass (kg), temperature ( Kelvin), etc. is makes easier for people from different countries to understand.
If we take the example of motion, where it is measured in meters as per International unit system if you like to say that I moved 4 m away from the chair. People who have an idea on what is a meter can only make a sense of what he says.
Hence, there is a need for an International System of Units to make sense of measurable scientific quantities to people from different countries.
