Final answer:
The abbreviation p.o. on a prescription means the medication should be taken by mouth.
Step-by-step explanation:
The abbreviation p.o. on a prescription stands for 'per os,' which means the medication should be taken orally by mouth. It is commonly used to indicate that the medication should be swallowed rather than injected or applied externally.
For example, if a physician prescribes 'Take one tablet p.o. twice a day,' it means the patient should take one tablet by mouth two times a day.