Geometry Foundations: Lines, Angles, and Transversals

Vocabulary flashcards covering basic geometric elements, angle classifications, parallel and perpendicular lines, and angles formed by transversals.

A geometric concept that has no length, width, or height, possessing neither size nor shape.

Point

A set of points that extends infinitely in opposite directions and does not have thickness.

Line

Two or more points that lie on the same line.

Collinear Points

Two or more points that do not lie on the same line.

Non-Collinear Points

Lines that meet at the same point.

Intersecting Lines

A flat surface that has infinite length and width, but no thickness.

Plane

A subset of a line that has one endpoint.

Ray

A subset of a line that has two endpoints.

Line Segment

A geometric figure formed by joining two rays at their endpoints.

Angle

The point where two rays meet to form an angle.

Vertex

The rays that make up an angle.

Sides

An angle measuring less than 90^\bar{\text{o}} but greater than 0^\bar{\text{o}}.

Acute Angle

An angle whose measure is exactly 90^\bar{\text{o}}.

Right Angle

An angle whose measure is greater than 90^\bar{\text{o}} but less than 180^\bar{\text{o}}.

Obtuse Angle

An angle whose measure is exactly 180^\bar{\text{o}}.

Straight Angle

An angle measuring greater than 180^\bar{\text{o}} but less than 360^\bar{\text{o}}.

Reflex Angle

Angles whose measures sum to 90^\bar{\text{o}}.

Complementary Angles

Angles whose measures sum to 180^\bar{\text{o}}.

Supplementary Angles

Two straight lines lying in the same plane that do not intersect and remain equidistant at all points; represented by the symbol \text{\|\|} (e.g., a \text{\|\|} b).

Parallel Lines

Two lines that intersect at a right angle, forming four 90^\bar{\text{o}} angles at their point of intersection; represented by the symbol $\bot$ (e.g., $CD \bot AB$).

Perpendicular Lines

A line, line segment, or ray that divides a line segment into two equal parts, passes through its midpoint, and forms a 90^\bar{\text{o}} angle with it.

Perpendicular Bisector

A line that intersects two or more lines at different points.

Transversal

Angles that lie between two parallel lines when cut by a transversal.

Interior Angles

Angles that lie outside two parallel lines when cut by a transversal.

Exterior Angles