# What are units of measurement?

Measuring, by definition, is a process of comparing the value of something we observe with some standard of measure we commonly agree to be our unit of measurement.

For instance, we commonly agree to measure a length by comparing it with a length of some object we agreed to be a unit of length. So, if the length of our object is 3 times greater than the length of the unit of length, we say that the measure of length of our object equals to 3 units of measurement.

Different objects of observation require different units of measurement. Unit of measurement of an area is different from unit of measurement of electric resistance. But for each type of observable object we have our own unit of measurement, so each object (time, weight, length, force, pressione, speed etc.) can be measured.

The most common system of units employed by the international scientific community is the International system of units (*Le Système international d'unités*, or SI). There are seven SI base units, and all physical quantities can be measured in terms of combinations of these seven units:

the meter for distance,

the kilogram for mass,

the second for time,

the ampère for electric current,

the kelvin for temperature,

the mole for amount of substance, and.

the candela for intensity of light.