AM: Anti Meridiem, PM: Post Meridiem
AM and PM both are Latin words, used in 12-hour clock system to represent Before Noon and After Noon respectively. They are also represented as A.M. and P.M.
AM expand as Anti Meridiem which means “before midday” and PM expand as Post Meridiem which means “after midday”.
They 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 6 O’clock so it may be confusing that it is 6 O’clock in the morning or 6 O’clock in the evening. Thus, to remove this confusion, AM and PM Pm is are used in 12-hour clock system. Accordingly, 6 am is early in the morning and 6 pm is late in the afternoon.
AM: It represents time from midnight to noon. (12:00 AM to 11:59 AM). For example: If you say that you have to go college at 10 AM, it means 10 O’clock in the morning.
PM: It represents time from noon to just before midnight. (12 Pm to 11:59 PM). For example: If you say that you have to take dinner at 10 PM, it means 10 O’clock in the night.