Fundamental Quantities in MKS System
The MKS system (meter-kilogram-second system) is a metric system of measurement based on three fundamental quantities: length, mass, and time. These fundamental quantities serve as the building blocks for all other physical quantities and units within the system.

Length
Length is a fundamental quantity in the MKS system and is measured in meters (m). It is used to quantify the extent of an object in one dimension. The meter is defined as the distance that light travels in a vacuum in 1/299,792,458 seconds.

Mass
Mass is another fundamental quantity in the MKS system and is measured in kilograms (kg). Mass is a measure of the amount of matter in an object and is independent of the object's location. The kilogram is defined by a specific platinum-iridium alloy cylinder kept at the International Bureau of Weights and Measures.

Time
Time is the third fundamental quantity in the MKS system and is measured in seconds (s). Time is a fundamental parameter for describing the sequence of events and is based on the vibrations of a cesium atom. The second is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.

Conclusion
In the MKS system, these fundamental quantities of length, mass, and time provide a solid foundation for measuring and quantifying various physical phenomena. By using these fundamental quantities as a basis, scientists and engineers are able to derive and define a wide range of derived quantities and units for describing the world around us.