Physics

The 17th General Conference on Weights and Measures (CGPM), 1983 has defined the meter as:

"The meter is the length of the path traveled by light in vacuum during a time interval of $2997924581 $ of a second."

Sub units of meter: (1) centimeter (cm), (2) millimeter (mm), (3) micrometer ($μm$) or micron, (4) nanometer (nm)

Metric System is further classified to SI system (Standard International System) and CGS (centimeter, gram and second system).

Foreg : In SI system,unit of length is metre denoted by "$m$" and $1m$ has 100 division. 1division $=1cm$(centimeter), which is the unit of length in CGS system.