👉 "Millimetres" is a term used in physics and engineering to describe units of measurement for measuring small changes in length or width. It is often abbreviated as "mm" or "μm." In this context, it refers to a unit of measurement that measures the thickness of an object without considering its volume. The millimeter is defined as the distance between two parallel lines intersected by a plane perpendicular to one of the lines and passing through the center of the other line. It has units