Millimeter (mm): The millimeter is equal to one one-thousandth of a meter (0.001 meters). It is frequently used for very precise measurements, such as the thickness of paper or the diameter of small objects.
Inch (in): The inch is equal to 1/12th of a foot or 0.0254 meters. It is used in various applications, including measuring the size of screens, paper, and some smaller objects.