General English


  • A unit of mass equal to approximately 0.0283495 kg. Also called avoirdupois ounce.
  • A unit of weight or force equal to the force of gravity on one ounce (1). This value varies by location, and is equal to approximately 0.278014 new-tons. Also abbreviated ozf, which is more proper than oz. Also called ounce force.


  • A unit of weight equal to one sixteenth of a pound. Still in use in the USA.


  • noun a measure of weight equalling 28 grams

Origin & History of “ounce”

English has two separate words ounce. The ‘measure of weight’ (14th c.) is etymologically the same word as inch. It comes from the same ultimate source, Latin uncia ‘twelfth part’, but whereas inch reached English via prehistoric Germanic, ounce’s route was through Old French unce. Its original use was in the Troy system of weights, where it still denotes ‘one twelfth of a pound’, but in the avoirdupois system it came to be applied to ‘one sixteenth of a pound’. Its abbreviation, oz (16th c.), comes from Italian onza.

Ounce (13th c.) ‘big cat’ comes from the same source as lynx (and indeed it originally meant ‘lynx’; ‘snow leopard’ is an 18th-century reapplication of the name). It represents an alteration of Old French lonce, based on the misapprehension that the initial l represented the definite article. this in turn came via vulgar Latin *luncia from Latin lynx, source of English lynx.