The symbol of length is L, which is a measure of one-dimensional space and the distance from point to point. Usually, when measuring the side length of a line segment in two-dimensional space, the one with a large length value is called long, which is neither greater than its value nor wider than the side length. So width is actually a measure of length, so measuring the height of "vertical length" in three-dimensional space is length.

The measurement of length is the most basic measurement, and the most commonly used tool is the scale. The international unit of length refers to the dimension length of space, and the unit is meter (m). Commonly used units are kilometer (km), decimeter (dm), centimeter (cm), millimeter (mm), micron (micron) and nanometer (nm). When converting length units, small units are converted into large units by multiplication and large units are converted into small units by division.

The use of length units

In measurement, a certain kind of quantity is taken as a reference quantity to determine how many times the known quantity is equivalent to the reference quantity, which is called a unit. For example, centimeter is the unit for measuring length, gram is the unit for measuring mass, and second is the unit for measuring time. As an example of mathematics, it can also be said that 1 is the unit of natural number, and the fraction with the numerator of 1 is the unit of fraction.

When measuring the length of a line segment, you need to select a line segment as the measurement standard and specify its length as 1, which is called the length unit. There are many units in length, the main unit is meter, and the rest are derived units. Select the appropriate length unit according to the actual needs when measuring. For example, the length of the runway is in meters, and the distance between two cities is in kilometers.