The mile is a unit of length in the metric system, equal to 1.60931 kilometers. It is also the basic distance unit used throughout the United States of America and many countries of the world. The word “mile” comes from the Latin word for “a thousand paces,” although its actual origins are still debated by scholars. The Romans used it to measure distances from one water source or naval station to another. Over time, other units were also derived from the mile, including the yard, league, foot and inch. Today, various definitions of the mile exist, but it is most commonly defined as 3,280 feet or 1.609 kilometers.

Millimeter is a unit of length that is one thousandth of a meter. It's often used in measurements to make them more understandable to the average person. Millimeters are also commonly used to describe the sizes and dimensions of things. Millimeter is the smallest unit of measurement in the International System of Units (SI). It is also called a subdivision of a centimeter. One millimeter is about the width of a human hair.