The Full form of AM is Anti Meridiem. AM is a Latin word, used in 12-hour clock system to represent Before Noon. It is also represented as A.M. AM expand as Anti Meridiem which means “before midday” and PM expand as Post Meridiem which means “after midday”. Both AM and PM are used to differentiate the time in day and night in the 12-hour time zone. They divide the 24 hours of a day into two time zones lasting 12 hours each. The first 12-hour duration runs from midnight to noon (12 am to 12 pm) and is designated by AM. The second 12-hour duration runs from noon to midnight (12pm to 12 am) and designated by PM. So, the numbers from 1 to 12 followed by AM or PM are used to identify all 24 hours of the 12-hour clock system. For example: If I say that I will come at 7 O’clock so it may be confusing that it is 7 O’clock in the morning or 7 O’clock in the evening. Thus, to remove this confusion, AM and PM are used in 12-hour clock system. So, 7 AM is early in the morning and 7 PM is late in the afternoon.