It is important to be well-versed with the common terms used in the chapter - lines and angles.Lines: It is a one-dimensional figure with no width but plenty of lengths. It is made up of a series of points that extend in opposite directions indefinitely. Two points in a two-dimensional plane are used to find it.Vertically Opposite Angles: When two lines cross, the opposite angles formed by the intersection are referred to as vertical angles or vertically opposite angles. A set of vertically opposite angles will always be equal.Linear Pair of Angles: When two lines intersect at a single point, a linear pair of angles is generated. If the angles are close to one another after the two lines intersect, they are called linear angles. Supplementary angles are the sum of angles in a linear pair that is always equal to 180°.