Transversal

A transversal is a line that intersects two or more other lines at distinct points. When it crosses parallel lines, it creates angle relationships used in geometry.

Line (geometry): A straight one-dimensional geometric figure extending infinitely in both directions. A transversal is itself a line and intersects other lines.
Corresponding angles: A pair of angles occupying matching positions at two intersections of a transversal with other lines. They are equal when the crossed lines are parallel.
Angle chasing: A method of finding unknown angles by combining geometric angle relationships. Transversal angle pairs provide the equations used to solve many diagrams.
Secant line: A line that intersects a curve at two or more distinct points. A transversal intersects lines, while a secant is defined by its intersections with a curve.
Angle: A figure formed by two rays sharing a common endpoint. Each intersection with a transversal produces angles to compare.
Alternate interior angles: A pair of angles between two lines and on opposite sides of a transversal. They are equal when the crossed lines are parallel.
Parallel postulate: Euclid's postulate asserting, in one formulation, that a unique parallel through an external point exists. Its consequences include the familiar angle rules for a transversal crossing parallel lines.
Perpendicular bisector: A line perpendicular to a segment at its midpoint. Unlike a general transversal, it is defined by a specific segment and two conditions.
Parallel lines: Coplanar lines that never intersect, however far they are extended. A transversal crossing parallel lines produces especially useful angle relationships.
Same-side interior angles: A pair of angles between two lines and on the same side of a transversal. They sum to 180 degrees when the crossed lines are parallel.

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