The mathematical units m, cm, dm_, cm_, m_, dm are meters, centimeters, decimeters squared, centimeters squared, square meters and decimeters respectively. The unit of length refers to the basic unit for measuring spatial distance, which is formulated by human beings to standardize the length.
Its international unit is "meter" (symbol "m"), and commonly used units are millimeter (mm), centimeter (cm), decimeter (dm), kilometer (km), meter (m), micron (micron) and nanometer (nm). Length units play an important role in various fields.