Which term is synonymous with "nothing by mouth"?

The term "NPO" stands for "nil per os," which is a Latin phrase meaning "nothing by mouth." This designation is used in medical contexts to indicate that a patient should not ingest anything orally, which is crucial prior to certain medical procedures, surgeries, or when specific medical conditions exist that prohibit oral intake.

The other terms listed have different meanings. "O.D." is an abbreviation for "oculus dexter," referring to the right eye, and it is not related to oral intake. "p.o." stands for "per os," indicating that medication or food should be taken by mouth, which is contrary to the concept of NPO. "O.S." refers to "oculus sinister," which pertains to the left eye, also unrelated to oral intake. Understanding these distinctions is important for clarity in medical settings and ensures proper patient care and communication.