Two lines are perpendicular if they intersect at a right angle. A line is perpendicular to a plane if it intersects the plane at a point and forms a right angle with any line in the plane passing through that point. A biconditional statement is a statement that contains the phrase "if and only if" and expresses a relationship that goes both ways between two conditions or events.

1. Terms of Endearment Definitions and Biconditional Statements: 2.2