The terms “AM” and “PM” are abbreviations used to distinguish between two 12-hour periods in a day, helping to indicate time more specifically in the 12-hour clock system. “AM” stands for “Ante Meridiem,” which is Latin for “before midday,” and it refers to the period from midnight to noon. “PM” stands for “Post Meridiem,” which is Latin for “after midday,” and it covers the period from noon to midnight. So, for example, 9:00 AM is in the morning, while 9:00 PM is in the evening.