**Following the acquisition of the abstract concept of number and its graphical representation, man needed to create a numbering or numeral system that would allow him to comfortably work with large quantities. To do this man needed to create a hierarchical system of multiple orders or levels, so that a certain number of units of a level were to become higher-level unit and so on. The criterion for organizing such a system is called “base”. So between us ten units are a set of ten and ten tens are one hundred or a century and ten hundreds are a thousand.**

The more widespread numeral system in the world is the base 10 system, we just instantiate, called "*decimal*" from the Latin word "*decem*" meaning "*ten*". But there are and have been other system, even among us. Relics of these other systems are for example counting by *dozens *in some cases (a dozen eggs …); it would correspond to a system or base 12, *duodecimal *or *duodenary*, from the Latin word "*duodecim*" which means "*twelve*"; the French phrase to designate 80 "*quatre vingt*" (four twenties) which reveals the use of *base 20*, measuring time: 60 *seconds *make a *minute *and 60 minutes an *hour* time corresponding to a *sexagesimal *system or base 60 (from Latin word *sexaginta *which means "*sixty*").

The decimal system is imposed naturally because ten are the fingers of the two hands that man used to tell. The hand is and remains the first calculating machine. However the systems of weights and measures in many countries, and even within them, were very different even being decimal, which greatly hindered relations, especially economic, between them.

At the end of the *Age of Enlightenment*, the eighteenth century, on the *French Revolution*, it begins to bring order to this confusion. First men tried to find a "unit" that was applied to the measurement of length, space, volume, capacity and weight. After much discussion was founded a length which is called "*metre *or *meter*" with which they built a pattern of platinum and iridium at 0 ° C. Today that distance is defined as the length of the path traveled by light in vacuum during 1/299.792.458 second.

This unit was called "*meter *or *metre*" from the Greek word ("μέτρον" *metron*) meaning "*measure*".

This unit could generate decimal multiples and submultiples, those who also had to put a name. The French scientists found a Solomonic solution: to multiples would put them Greek names: *deca*-, from the Greek "*deka*" (δέκα), which means ten, *hecto*-(Greek ἑκατόν "*ekaton*") meaning hundred, *kilo*-(χίλια Greek. "xilia") which means thousand. To sub-multiples Latin names would be placed: *deci*-(from the Latin "*decem*" meaning “ten”, *centi*-(Latin *centum*) meaning *hundred*, cent,; *milli*-(from the Latin "*mille*") which means “thousand”.

Applying this terminology to length measurements we have: the unit is the *meter*; multiples are *decameter or decametre, the hectometer, kilometer*, submultiples are *decimeter, centimeter, millimeter. *

As measure of capacity we the *liter*; multiples the *decaliter, the hectoliter, kiloliter*; submultiples *deciliter, centiliter, milliliter*.

The word "*liter*" is from the French "liter" and this from medieval Latin "*litra*" and this in turn from the Greek λίτρα, "*litra*" meaning and from which “*libra*”, on English "*pound*".

As weight measures we have the unit, *gram *(Greek γράμμα, "*gramma*" meaning *letter *and passing into Latin with the meaning of *pebble*); are multiples *dekagram, hectogramme or hectogram, kilogram*; submultiples are *decigram, the centigram, the milligram.*

Once again Greece and Rome, our roots, came to our aid.

By the way, a prism with 1 decimeter base by a decimeter height is a cubic decimeter because it results from multiplying 3 times the decimeter (length X width X height). The capacity of water that can collect this prism is a *liter *and the weight of that water is one *kilogram*. It was thus the relationship and equivalency among the measures of length, capacity and weight and all of them on the decimal system. Besides was the measurement of time, as noted ancient residue.

So has be imposed almost entirely the decimal system except the relics previously mentioned, and in the Anglo world, determined to count in *miles *and *yards*.

Both in the case of relics like English is checked once more that in human society is not always forced coldly rational; they are manifestly improvable customs imposed by the will or social inertia.

But the needs of modern computing has forced to overcome traditional metric system and this has created the International System of Units or multiples measures with terms such as yotta, zetta, exa, peta, tera, giga, mega, kilo, hecto, deca, and submultiples such as deci, centi; milli, micro, nano, pico, femto, atto, zepto, yocto .

Almost all the new names are also Greek and Latin with some adaptations, as yotta, zetta, peta (like penta), giga, mega … micro, nano, micro, zepto, yocto. It seems to have cast some Danes as femto or attto.