Final answer:
'ac' stands for 'before meals' in medical prescriptions, guiding when medication should be taken relative to mealtimes.
Step-by-step explanation:
The abbreviation "ac" in a medical context commonly stands for 'before meals'. It is derived from the Latin phrase 'ante cecum', which means before meals. This term is typically used in prescribing medication to indicate that the medication should be taken before a patient eats. It's one of several Latin abbreviations that are used in medical prescriptions to communicate when and how often medications should be taken by the patient.
Other common abbreviations include 'pc' for after meals (post cecum), 'prn' for as needed (pro re nata), and 'stat' for immediately (statism).