\( \overleftrightarrow{A B}=\overleftrightarrow{X Y} \overleftrightarrow{A B} \left\lvert\, \overleftrightarrow{X Y} \quad \begin{array}{c}\text { Which of the } \\ \text { following means } \\ \text { these lines are } \\ \text { parallel? }\end{array}\right. \)

When you see the symbol \( \overleftrightarrow{A B} \parallel \overleftrightarrow{X Y} \), this notation indicates that the line segment \( \overleftrightarrow{AB} \) is parallel to \( \overleftrightarrow{XY} \). Parallel lines share the same slope and will never intersect, no matter how far they are extended. In geometry, understanding the concept of parallel lines is crucial, especially when working with angles and transversals. For instance, when two parallel lines are crossed by a transversal, several pairs of angles are formed – such as corresponding angles, alternate interior angles, and consecutive interior angles – that have specific relationships. Utilize these relationships in geometric proofs to solidify your mastery of the topic!