Selective serotonin reuptake inhibitor. Selective serotonin reuptake inhibitors (SSRIs), also known as serotonin-specific reuptake inhibitors or serotonergic antidepressants,[1] are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder and anxiety disorders.
Then you're looking for the midpoint! The midpoint of a line segment is the point located midway between the endpoints of the line segment. This tutorial tells you about the midpoint of a line segment.
An endpoint is a point at one end of a segment or the starting point of a ray. A capital letter. A ray is a part of a line that starts at an endpoint and extends forever in one direction. Its endpoint and any other point on the ray. Opposite rays are two rays that have a common endpoint and form a line.