What is the meaing of "the eastern half "?

Does it mean " all the eastern part " or the half of the eastern part??

Thanks for reading.
It probably means all the eastern part. More context might prove me wrong, but I doubt it.
It means the half of the [whatever - nation, bay, city] that is on the eastern side.

Almost the entire eastern half of the nation experienced terrible weather last week. The eastern half of of the bay shorline is highly developed, but the western side is still quite rural.
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Full sentence is "It is founded in the eastern half of North America".
So do you understand what it means now or do you still have questions?
Grammar Geek,

I wrote down full sentence to save confusion .. I think that Philip's opinion and yours are different.

so you mean that eastern half of North America is the half of the eastern part of North America??
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Hi Darcy

Philip and GG's opinions are the same.
Look at this picture:

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The red line in the middle separates (approximately) the eastern half from the western half of the North American continent.

When someone uses the word half in an expression such as "the eastern half of North America", it is not usually intended to be a precise measurement but rather a rough approximation.
The picture is perfect to make me understand..thanks a lot.

Philip,Grammar Geek,Yankee.. thank you so much again.