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.

The yard is the traditional length unit of linear measure. It is traditionally equivalent to 0.9144 meters, though it has been varied between 9 and 12 feet in recent times. The yard was first conceptualized by fifth-century BC Egyptians and was standardized as 9 feet in 1795 by the French military engineer General Hoche. During the American Revolutionary War, the Continental Army was unimpressed with various proposals for a new foot measuring system and instead adopted the British yard as their standard. The use of the yard spread rapidly throughout the world after that due to its international compatibility. Today, most countries use either the metric system or a variant of it, and there are few remaining areas where yards are used; Africa mostly uses meters, India uses centimeters, parts of Asia use traditional units like li and fen.