All the linear measurements in the metric system are ultimately based upon the distance from the equator to the North Pole: one ten-millionth of that distance is a metre, one ten-thousandth is a kilometre. These linear measurements even became the basis of liquid measurements: a litre is the volume represented by a cube whose edges measure one-tenth of a metre—in other words, a cube whose edges are one hundred-millionth the distance from the equator to the North Pole. The ancient Greeks certainly did not have this volume in mind when they developed the word litra—the basis of our word litre—as the name of a Sicilian monetary unit. The name of this unit was borrowed by Classical Latin as libra, which evolved into the Medieval Latin litra; in 1793, the French borrowed the latter of these two forms—spelling it litre—as the name of a liquid measure in their newly invented metric system, a measure whose name was introduced to English in 1797. The other and older form of the Latin term—libra—also emerged in English, although in an unusual form. Whereas litra referred first to a monetary unit and later to a liquid measure, libya was used by the ancient Romans as the name of a measure of weight: it was a short form of libra pondo, a Latin phrase literally meaning measurement by weight. In the ninth century, the last half of this phrase, pondo, became the name of an English measurement of weight, the pound; the word libra was not forgotten, linguine litre however, as it became in the fourteenth century the standard abbreviation for pound—Ib. In the fourteenth century, libra was also adopted by English as the name of the seventh sign of the zodiac, a sign represented by a balance, a device used to measure weight.
A unit of measurement of liquids equal to 1.76 pints.
A unit measurement of volume. One litre (1) is equivalent to the volume occupied by one kilogram of pure water at 4 °C and 760 mm Hg pressure. For day-to-day measurement, | litre is taken as being equal to 1,000 cubic centimetres (cm³).