What is the unit of length? How to express it in letters?

Commonly used length units are: kilometer {kilometer} (km), decimeter (dm), centimeter (cm), millimeter (mm), micron (micron), nanometer (nm), picometer (pm) and femto meter (fm).

(1) km

Kilometer, also known as kilometer, is a unit of length, abbreviated as "km", which is usually used to measure the distance between two places. The common conversion relationship is as follows: 1 km (km) = 1 0,000m (m) = 1 00,000m (cm) =10,000mm (mm); 1.6 1 km = 1 mile.

(2) meters

The unit of length "meter" in the international system of units originated in France. 1790 In May, a special committee composed of French scientists suggested that one fortieth of the total length of the earth meridian passing through Paris should be used as the unit of length-meter, and 179 1 year was approved by the French Parliament.

(3) decimeter

Decimeter or dm is one of the metric units of length, and 1 decimeter is equivalent to one tenth of 1 meter. The common conversion relationship is as follows: 1 decimeter = 0.000 1 kilometer (km) = 0. 1 meter (m) = 10 centimeter (cm) = 100 millimeter (mm).

4) cm

Centimeter, unit of length; Chinese: centimeter (s), abbreviated as cm. The unit conversion of centimeters is as follows:1cm =10 mm = 0.1decimeter = 0.0 1 m = 0.0000 1 km.

(5) mm

Millimeter, also known as millimeter (or millimeter), is a unit of length and rainfall, and the symbol is ㎜. 1mm is equivalent to one thousandth of 1mm (this means "milli"). The decimal relation is as follows:1mm = 0.1cm = 0.01decimeter = 0.001m = 0.000001km.