Parallel lines never intersect and have the same slope.

Perpendicular lines intersect at 90 degrees. One line's slope is the opposite reciprocal of the other's.

Two coplanar lines that intersect.

Dotted lines represent hidden portions of the plane.

Two planes intersect in a line.

Any line that contains A and is on the plane is perpendicular to line AB.

Line intersecting a plane at point A. The dotted portion of the line is occluded by the visible part of the plane.

Angles formed by two lines cut by a transversal. The lines do not appear parallel in this diagram, but you are free to constrain them if needed.