I know it's a silly question, but it really bothers me since the word hemisphere derives from Greek ημί- (i.e. hemi-) which cannot be further expanded, while the English equivalent semi- can be further expanded to quarter-.
So, my question has three parts:
- Firstly, does the choice of "hemi-" instead of "semi-" only from geology or is it used as such in mathematics in the same manner?
- If the Earth were instead flat, would we refer to a hemicircle or semicircle?
- If I want to refer to the northwestern part of Earth, what's the correct word, since hemisphere is obviously wrong?
Thank you in advance