Oncia

Oncia is the Italian term for ounce, a traditional unit of measurement used in various systems. The word derives from Latin uncia and entered Romance languages through medieval usage. In modern Italian, oncia most often denotes a unit of mass, but it can also appear in contexts referring to liquid volume as oncia fluida, particularly in historical or specialized texts.

In terms of mass, the oncia has two principal meanings depending on the system:

- The avoirdupois ounce, equal to 28.3495 grams, with 16 oncie per pound. This is the standard ounce used for most everyday measurements in countries that follow the avoirdupois system.

- The troy ounce, used for precious metals, equal to 31.1035 grams; there are 12 troy ounces per troy pound. In bullion markets, the oncia or oncia troy is often implied to be the troy ounce, sometimes abbreviated oz t.

For liquids, the fluid ounce is a separate measure. In US customary units, 1 US fluid ounce equals 29.5735 milliliters; in the British imperial system, 1 imperial fluid ounce equals 28.4131 milliliters. When Italian texts specify oncia fluida, they are referring to one of these liquid-volume standards in a historical or specialized context.

Current usage: Italy and much of Europe have metricated weights and volumes, so oncia is largely found in historical references, specialized trade, or consumer contexts such as perfumery or antique coinage. In everyday life, metric units (gram, liter) are preferred.

Notes: Oncia differs from onza in Spanish and from the English ounce. In bullion trading, oncia is commonly understood to mean the troy ounce.