The smaller U.S. standard basic units of length are the inch, foot and yard. A foot is twelve
inches and a yard is 3 feet or 36 inches.
Many measurements are made that are less than one inch and for these the U.S.
system of measurement uses fractions of an inch (1/2, 1/4, 1/8, 1/16 etc.)
There are other units for measuring small lengths but they are used only in
specialized areas (mils, points, picas etc.)