Mathematics Grade 9: Undefined Terms and Geometric Constructions

A set of vocabulary flashcards covering basic geometric terms, line subsets, and the principles of geometric construction as presented in the Grade 9 Mathematics Lesson Exemplar.

Point

A geometric element that has no size and dimension.

Line

A geometric figure made up of points that has no thickness or width.

Plane

A flat surface that extends without end in all directions.

Collinear

A term describing points that lie on the same line.

Undefined Terms

The most basic terms in geometry, specifically point, line, and plane, which are understood through their properties rather than defined by other terms.

Ray

A part of a line that has a definite starting point called an endpoint and extends without end in one direction.

Line Segment

A part of a line that has a definite beginning and end, characterized by having two endpoints.

Opposite Rays

Two rays that are part of the same line and have only their endpoints in common.

Angle

A figure formed by two rays that have a common endpoint but are not part of the same line.

Vertex

The common endpoint of the two rays that form an angle.

Sides of the angle

The two rays that make up an angle.

Construction

A geometric drawing created using a limited set of tools, specifically a straightedge and a compass.

Straightedge

An object used to draw a straight line, such as a ruler, a credit card, or a piece of cardboard.

Compass

A tool used for drawing circles or arcs, or for marking off equal distances in geometric constructions.

Perpendicular Lines

Two lines that intersect to form a right angle.

Parallel Lines

Coplanar lines that do not intersect and maintain a constant separation.