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.
To construct a midpoint, first select the Midpoint tool from the DRAW menu (press [GRAPH][WINDOW], repeatedly press. to highlight the Midpoint tool, and press [ENTER]). If you are constructing the midpoint of a segment, use the arrow keys to place the cursor on the segment and press [ENTER] to construct the midpoint. If you are constructing the midpoint between two points, move the cursor to the first point and press [ENTER].