Subject: Geometry
Line Types
Intersecting lines
Lines are said to be intersecting if they meet at a common point.

\overleftrightarrow{AB} and \overleftrightarrow{CD} intersects at point (1, -1)
Parallel Lines
Lines are said to be parallel if it does not intersect or meet at a certain point on the same plane (co-planar). The relationship is symbolized with " || " between the line names. Suppose, \overleftrightarrow{AB} is parallel to \overleftrightarrow{CD} . It will be written as \overleftrightarrow{AB} || \overleftrightarrow{CD} .

\overleftrightarrow{AB} || \overleftrightarrow{CD} .
Perpendicular Lines
Lines are said to be perpendicular, if a line intersects another line forming a right angle. The relationship is symbolized with " ⊥ " between the line names. Suppose \overleftrightarrow{AB} is perpendicular to line \overleftrightarrow{CD} , it will be written as \overleftrightarrow{AB} ⊥ \overleftrightarrow{CD}

\overleftrightarrow{AB} ⊥ \overleftrightarrow{CD} .
Transversal Lines
A line is said to be transversal if it goes across two lines which are usually parallel. If it crosses parallel lines it is called ''perpendicular transversal."

perpendicular transversal

non-parallel case
