It is used in words to indicate that something is partially or incompletely formed, divided into two parts, or relating to one half of something.
Here are some examples:
* Hemisphere: Half of a sphere
* Hemiplegia: Paralysis of one side of the body
* Hemicrania: Headache on one side of the head
* Hemiparesis: Weakness on one side of the body
* Hemicolectomy: Surgical removal of half of the colon
In some cases, "-hemi" can be used to describe something that is smaller than normal or partially developed.
For example, a hemihypertrophy is a condition where one side of the body is larger than the other.
So, when you see "-hemi" in a word, you know that it's referring to something that is half, partial, or incomplete.