Ounce (noun)

1. A unit of weight of one sixteenth of a pound avoirdupois (approximately 28 grams).
2. A unit of fluid measure of one eight of a pint (approximately 30 milliliters).

Origin:

Middle english: from old french unce, from latin uncia "twelfth part", used as a weight term.

Examples:

1. The gold bar weighs an ounce.
2. He bought an ounce of weed.
3. The recipe calls for an ounce of chocolate.
4. The baby was born weighing 7 ounces.
5. She poured an ounce of oil into the pan.