'Prescribe' is Latin for 'write before' — which is precisely what a medical prescription does.
To lay down authoritatively as a rule or guide; in medicine, to advise and authorize the use of a particular treatment or medication.
From Latin 'praescribere' meaning 'to write before, to write at the head of, to order in advance,' composed of 'prae-' (before) and 'scribere' (to write). In Roman law, 'praescribere' meant to write a preliminary clause or set a prior condition. The medical sense — a physician writing an order for medicine — appeared in English by the sixteenth century, drawing on the image of the doctor writing instructions before the pharmacist prepares the remedy. Key roots
The symbol 'Rx' at the top of medical prescriptions is not an abbreviation of 'prescription' — it derives from the Latin word 'recipe,' meaning 'take' (the imperative form of 'recipere'). Medieval physicians would begin their written instructions to apothecaries with 'Recipe:' followed by the ingredients. The R gradually acquired a crossed