Why is the word pound (as in weight) abbreviated as 'lbs'?

The abbreviation "lbs." certainly seems like a strange way to write "pounds," until you consider the origin of the word. Like many terms used in science, the word "pound" has a Latin background. It comes from "libra pondo," the Latin expression for a "pound of weight." The English word "pound" comes from "pondo," and the abbreviation "lb." comes from "libra." When you are referring to more than one pound, an "s" is added to the abbreviation to make it plural, so it becomes "lbs."

The pound as it is used in the US (and was used in other places) works out to be close to the old Roman unit of measurement known as a "libra" (which is related to the zodiac symbol of scales). The "lb" abbreviation was adopted long ago as a way to keep the weight measurement distinct from the money unit that was also known as a pound (the money type of pound used to be equal to a weight pound of silver).

The origin is in the Latin word libra, which could mean both balance scales (hence the symbol for the astrological sign Libra, which was named after a constellation that was thought to resemble scales) and also a pound weight, for which the full expression was libra pondo, the second word being the origin of our pound.

Latin Word For Pound