relating to or characteristic of regions of eastern parts of the world
"Eastern Europe"
"the Eastern religions"
Of, facing, situated in, or related to the east.
"From our viewpoint in London, the bustling metropolis lies far to the east."
Of a region designated as the East by convention or from the perspective of the speaker or author.
In plain English: Eastern means being on the right side of the world when you look at a map with north at the top.
"The eastern side of the house always gets more sunlight than the rest."
Usage: Use eastern to describe something located in a direction that is right before south when facing north, or specifically within regions defined as the East relative to your current viewpoint. Avoid using it for anything simply happening in the morning, as that refers to time rather than geography.
The word eastern comes from the Old English ēasterne, which originally meant "of or pertaining to the dawn." It traveled into modern usage through Middle English while retaining its core meaning of relating to the direction where the sun rises.