Meaning

noun a measured portion of medicine taken at any one time

noun the quantity of an active agent (substance or radiation) taken in or absorbed at any one time

noun a communicable infection transmitted by sexual intercourse or genital contact

originBorrowed from Middle French dose, from Late Latin dosis, from Ancient Greek δόσις (dósis, “a portion prescribed”, literally “a giving”), used by Galen and other Greek physicians to mean an amount of medicine, from δίδωμι (dídōmi, “to give”). Doublet of doos.

Etymology from Wiktionary, CC BY-SA 3.0