This is a question of terminology.
Suppose we have a line segment AB in a plane. The line segment forms three "zones" in the plane, where the "middle zone" is comprised of points for which some line perpendicular to AB passes through both that point and AB.
Is there a name for this "middle zone"? I want to be able to make a concise statement such as:
Point P is ___ to / in the ___ of the line segment AB.
The reason for my asking is that I'm writing a software function which tests for this quality (I already know how to do this - that's not the question,) and I need to figure out what I should be calling this function in order for its purpose to be clear to other people.
That is, what is the name of the gray zone in this picture:
(Normally web searches answer all my math questions, but it's hard to search what to call something!)