X is the most important letter of the alphabet in medicine, because of its common use in abbreviations. Use ranges from the straightforward “Polio x3” for three polio vaccinations, to “Discharged to Ward X,” a common euphemism for the morgue. But there are many others: dx is diagnosis; px, prognosis; Rx, therapy; sx, symptoms; hx, history; mx, metastases; fx, fractures.
