One-dimensional example: A semi-infinite medium is a medium that extends to infinity in one direction but has an end in the other direction

If the domain is infinite, any polynomial of odd degree has infinite range whereas a polynomial of even degree has a semi-infinite range.

Semi-infinite means that either the range has a real minimum but no maximum (ie maximum = +infinity) or that it has a real maximum but no minimum (ie minimum = -infinity).

Geometry teaches there are an infinite number of semi-circles for a sphere. Hence in the grid system that creates the longitude lines that form semi-circles, it becomes the same as what is taught in geometry = infinite number.

If you limit yourself to using a llimited definition to units of whole degrees, then 360 semi-circles. However, I suspect that the answer you need is Infinite.

There are an infinite number of points on the circumference of a circle and an infinite number of points on a semi-circle so the answer to your question is "An infinite number of pairs of points."

Two: a straight line and a curved line.