1. The amount of a therapeutic medication, or other substance, that is administered in a prescribed and measured amount at any one time: The dosage was clearly indicated on the label of the medicine bottle.
2. In winemaking terminology, the addition of sugar to specific wines: The wine taster determined that a slight dosage of sugar would be appropriate to add to the wine before corking.
3. Etymology: from Middle French (about 1400-1600) dose, from Late Latin dosis which came from Greek dosis, "a portion prescribed"; literally, "a giving".

Used by Galen and other Greek physicians to mean "an amount of medicine", from Greek didonai, "to give".