The abbreviation 'lb.' (pound) originates from the Latin word for 'scales' (libra).

The pound or pound-mass is a unit of mass used in the imperial, United States customary and other systems of measurement. The libra (Latin for 'scales' or 'balance'), is the origin of the abbreviation for pound, which is lb.

In ancient Rome a pound was a mass that was equivalent to approximately 328.9 grams. It was divided into 12 'uncia', or ounces. In Latin 'lb' indicates both the singular and the plural of the measurement and the commonly used abbreviation 'lbs' to indicate plural is a modern development.

A number of different definitions of the pound have been used in Britain. Among these are the avoirdupois pound and the obsolete tower, merchants', and London pounds. The pound sterling used to be a tower pound of silver, but the standard was changed to the Troy pound in 1528.

In the United States, the pound has been officially defined in terms of the kilogram since the Mendenhall Order of 1893. That declared the pound to be 2.20462 pounds to a kilogram. In 1894 this relationship was, however, refined as 2.20462234 pounds to a kilogram, following a determination of the British pound.

Countries of the Commonwealth of Nations agreed upon common definitions for the pound and the yard. Since 1 July 1959, the international pound has been defined as exactly 0.45359237 kg.