What is ante - meridian?

Answer 1

An Anti-Meridian is a meridian opposite any given meridian of longitude.

Specifically the Anti-Meridian is the 180th meridian. That is the meridian opposite of the Prime Meridian.

The term Anti-Meridian is sometimes confused with Ante Meridiem.

Ante Meridiem is latin for before noon. Usually shown in English as "a.m.". Similarly, post meridiem, after noon, is shown in English as "p.m.".

Answer 2

It means before noon and postmeridian means after noon.

Answer 3

An antimeridian is a reference line at 180 degrees longitude, on the opposite side of the Earth to the prime meridian.

Answer 4

Ante meridian (a.m.) refers to the time before noon, typically between midnight and noon. It is used to distinguish time in the morning from time in the afternoon (post meridian, or p.m.).