Geometry: Undefined Terms and Subsets of a Line

Flashcards covering the foundational undefined terms of geometry and subsets of a line, including points, lines, planes, rays, line segments, and angles.

Undefined terms

Terms that do not require a definition but can be described; they are used as a base or building blocks to define other mathematical terms.

Point

A geometric concept that has no size and dimensions.

Line

An undefined term made up of points that has no thickness or width and features an arrow head at each end; it can be named as Line $p$, $\overleftrightarrow{AB}$, or $\overleftrightarrow{BA}$.

Plane

A flat surface that extends without end in all directions; can be named as Plane $m$, Plane $PQR$, or Plane $RQP$.

Ray

A subset of a line that has a definite starting point (called an endpoint) and extends without end in one direction; it can be named as Ray $AB$ ($\overrightarrow{AB}$) or Ray $ST$ ($\overrightarrow{ST}$).

Line Segment

A part of a line that is bounded by two distinct endpoints and has a fixed length; it can be named Line segment $AB$ ($\overline{AB}$) or Line segment $BA$ ($\overline{BA}$).

Angle

A figure formed by two rays that have a common endpoint but are not part of the same line; it can be named as $\angle ABC$, $\angle CBA$, or $\angle 1$.

Vertex

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

Sides

The two rays that make up the angle.