A straight line passing through the midpoint of a line segment and perpendicular to the line segment is called the midline of the line segment.
A straight line passing through a point perpendicular to another straight line is called a vertical line.
The length of the line segment between two points is called the distance between two points.
A vertical line perpendicular to a straight line is called the distance from a point to a straight line.
A point on a straight line perpendicular to parallel lines is called the distance between these two parallel lines.
A ray from a vertex of a triangle divides the angle into two equal angles, which is called the bisector of the triangle.