The term 'Ruler Measure' refers to the units of measurement used to measure length. The most common units of measurement are millimeter (10 letters), INCH (4 letters), and onefoot (7 letters). Millimeters are the smallest unit of measurement, equal to one thousandth of a meter. Inches are slightly larger than millimeters, and are equal to one twelfth of a foot. Onefoot is the largest unit of measurement, equal to twelve inches or one third of a yard.