Imperial units are the traditional units of measurement. In
many countries they have now been replaced by metric units.
In imperial units length is measured in inches, feet, yards,
miles; mass is measured in ounces, pounds, stones, hundredweights,
tons; capacity is measured in pints, quarts, gallons.
units were introduced in the United Kingdom and its colonies,
including Commonwealth countries (most have since become officially
metric, but continue to use both Metric and Imperial), but
excluding United States. Systems of imperial units are sometimes
referred to as foot-pound-second, after the base units of
length, mass and time.