The meter is the SI unit for measuring length.
When it comes to taking measurements, some terms can be confusing when comparing quantities. A system of standards must be in place in order to properly quantify a measurement. The international system of units (SI) came into being on Jun. 22, 1799 in France, when two platinum standards were agreed upon as the universal representations of the meter and the kilogram.
Definitions
To understand the international system of units, you must first learn the definitions of some basic terms. In particular, the terms "quantity" and "unit" must be defined before we can standardize against them. Quantity is a property of a scientific phenomenon that is quantifiable or assignable. The mass of your laptop and the diagonal measure of its screen are two examples of quantity. Unit is a particular type of physical quantity, according to the National Institute of Standards and Technology, which is used as a convention to compare measures.
Units of Length
Length is a base unit of the SI. This means it is not composed of separate measurements, such as speed's SI unit of meters per second, or density's kilogram per cubic meter. There are a multitude of measures of length, some used more than others. For instance, fathoms, rods, cables, leagues and furlongs are units not often used when discussing an object's length. More often, metric and Imperial units are used, including inches, feet, miles, centimeters, meters and kilometers.
SI Base Unit of Length
The meter is the SI unit of measure for length. Many Americans are not terribly comfortable using SI units, as they have not been taught the metric system, so they must convert between the two. For example, if a 6-foot tall man wants to express his height in SI units, he must convert between feet and meters. One foot is equal to 0.3048 meters, so he would need to multiply 6 by 0.3048 to get 1.8288 meters.
Derived Units
Once you have the SI base unit for length, you can find other units. For example, the SI unit for speed is derived from the SI units for length and time, which are meters and seconds, respectively. Any other SI quantity that is dependent on length will use meters in the unit, either as a multiplier or denominator. When abbreviating meters, it must always be done with a lower case m and never pluralized.
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