To understand what is the **metric system** , you have to know what the idea of **unit system** : it is a group of **measurement units** . A unit of measure, meanwhile, is a **quantity** of a **certain magnitude** physics that is defined, standardized and adopted in a conventional manner.

With this clear, we can move forward and say that the **metric system** is a **unit system** what is it like **base unit of measure** to the **subway** . This unit of measure is a unit of **length** (the physical magnitude that indicates the amount of space that exists between two points: that is, the **distance** ).

Let's review all these notions so that it is clear what the metric system is. Units of measurement refer to quantities of physical quantities. These **units** they form sets that are known as unit systems. Among the different unit systems, is the metric.

The particularity of the metric system, as mentioned above, is that it is based on the unit of measure known as **subway** . Said unit, and therefore the entire metric system, is used to name the physical magnitude known as distance.

The meter is defined as the distance traveled by the **light** at **empty** in a temporary period of **1/299 792 458 of a second** . When the metric system relates the units of measure by **multiples** and **submultiples** from **10** , it is called **metric system** (considered as the oldest unified measurement system).

Those that we have exposed are the measures that are used to carry out the measurement of the length, nevertheless, we cannot ignore that there are others that are used to undertake the same thing but with the mass, the capacity, the surface ... to understand it, nothing better than to see some examples:

-To measure the mass, we come across the fact that the measure is the gram and then there are units larger or smaller than it, such as the kilogram (1,000 grams) or the decigram (0.1 gram).

-To proceed to measure the capacity, on the other hand, we come across the liter as a “basic” measure and then from there other units such as hectolitre (100 liters), deciliter (0.1 liter), kiloliter (1,000 liters) ...

-In the case that you want to measure what the surface is, the metric system bets on square meters: m2, which is the fundamental unit. From this, other units are already created, such as the square kilometer (km2), which are 1,000,000 m2 or the square diameter (dam2), which corresponds to 100 m2, among others.

-Of course, do not forget the cubic meter (m3), which is the unit used to carry out the volume measurement. It should be stressed that, as in the cases cited above, there are also other measures that are greater or less than that cited. Thus, there are, for example, the cubic decimeter (dam3), which responds to 1,000 m3, or the cubic decimeter (dm3), which is equivalent to 0.001 m3.

The establishment of the decimal metric system as **universal system** it took place in **1875** and contributed to the development of commercial and scientific exchange, by establishing the same unit of measure for all **countries** . It is important to note that until that moment, there was a different system of units in each country (and, often, in each of its regions) than the rest; even, the same name could come to represent different values in each place, or vary its meaning over time.

A clear example of the lack of consistency between the units of measure that took place before the emergence of the metric system can be seen by observing the known length measurement with the name of **rod** , which has an equivalence for its Castilian version (0.8359 meters), and another for its Aragonese version (0.7704 meters).

One of the most obvious characteristics of the decimal metric system is that it has a system of notations to distinguish between several of its multiples and submultiples, something that arose to end the lack of order that existed between the first systems of **measurement** , which did not use multiples and decimal submultiples, nor did they have a consistency in the choice of their names, thereby generating confusion and complications when using them to perform mathematical calculations.

To construct the name of each of the multiples and submultiples of the decimal metric system, simply prefix the word "meter", and thus obtain the following terms: **decameter** (10 meters); **hectometer ** (100 meters); **kilometer ** (1,000 meters); **mymeter ** (10,000 meters); **decimeter ** (one tenth of a meter); **centimeter ** (one hundredth of a meter); **millimeter** (one thousandth of a meter). There are others **values** which are also distinguished by prefixes, both larger than the mymeter and smaller than the millimeter, although they emerged much later than these and are not as well known outside the scientific field.

In spite of the attempts of the human being to establish universal parameters for the measurement of the diverse magnitudes, there are still too many units of measurement and exceptions so that a person can spontaneously understand the values that are found when leaving his country. When someone accustomed to the metric system faces the **mile** or to **feet** For example, it is normal that you do not know the equivalences.