A Latin instruction, abbreviated a.c., meaning before food, written on prescriptions to indicate that a medicine should be taken before meals. The timing matters pharmacologically: some drugs absorb better on an empty stomach, some must precede food to protect the stomach lining or to be present when nutrients arrive, as with certain diabetes medications taken before eating to blunt the post-meal glucose rise. Pharmacists translate the abbreviation into plain language for patients, since misunderstanding timing instructions is a common cause of treatment failure. The persistence of Latin in prescribing is a historical inheritance from when it was medicine’s universal language, and modern practice increasingly favors clear vernacular instructions. Whatever the wording, the principle stands: when a drug meets food can determine whether it works.