Dosage is the amount of a medicine or other drug you are meant to take at one time — especially when you take it regularly. The bottle or the doctor gives the dosage: one tablet twice a day, or 5 ml every four hours. People sometimes stretch it to mean “how much of this you use,” but the home meaning is medicine. It is a slightly formal, medical word; at home a parent may just say “how much” or “the dose.” Dose and dosage sit close together: a dose is often the single amount you take now; dosage can mean that too, but it also covers the whole plan (how much and how often).