1.2 - Points, Lines, and Planes

Vocabulary flashcards covering the definitions, notation rules, and diagrams for points, lines, planes, segments, rays, collinear points, and coplanar points.

Point

The simplest figure in Geometry. Technically does not have any size.

Line

One-dimensional, extends infinitely.

Plane

Two-dimensional, extends infinitely. Examples include a piece of paper, a tabletop, a flat wall, or the ground.

Line Segment (segment)

Consists of two endpoints and all points in between.

Ray

Consists of an initial point and all points to one side.

Opposite Rays

Rays that share an initial point and extend in opposite directions.

Collinear Points

Points that lie on the same line.

Coplanar Points (figures)

Points (figures) that lie on the same plane.

Point Notation Rule

Represented using $1$ upper-case letter.

Line Notation Rule

Represented using $2$ capital letters with an arrow on top. Order of letters does not matter and can be any $2$ points on the line.

Plane Notation Rule

Varies. Can be $1$ italicized upper-case letter, sometimes $3$ upper-case letters with no symbols, or sometimes a cursive lowercase letter.

Line Segment Notation Rule

Represented using $2$ capital letters with a line segment on top (no dots, no arrows). Letter order does not matter, but letters must be the endpoints.

Ray Notation Rule

Represented using $2$ capital letters with a ray (always points right) on top. The $1\text{st}$ letter must be the initial point, and the $2\text{nd}$ letter can be any other point on the ray.