Point
A point is a location. It has neither shape nor size.
Line
A line is made up of points and has no thickness or width. There is exactly one line through any two points.
Plane
A plane is a flat surface made up of points that extends infinitely in all directions. There is exactly one plane through any three points on the same line.
Collinear points
Points that lie on the same line. Noncollinear points do not lie on the same line.
Coplanar points
Points that lie in the same plane. Noncoplanar points do not lie on the same plane.
Intersection
The intersection of two or more geometric figures is the points they have in common. Two lines intersect in a point. Lines can intersect planes, and planes can intersect each other. Planes intersect in a line.
Definitions/defined terms
Definitions or defined terms are explained using undefined terms and/or other defined terms.
Space
Space is defined as a boundless, three-dimensional set of points. Space can contain lines and planes.
Line segment
A measurable part of a line that consists of two points, called endpoints, and all of the points between them.
Between/Betweeness of points
For any two points A and B on a line, there is another point C between A and B if and only if A, C, and B are collinear and AC + CB = AB
Congruent
Having the same measure
Ridgid transformation
A transformation in which the position of the image may differ from that of the preimage, but the two figures remain congruent.
Congruent segments
Two segments with the same measure
Constructions
A method of creating geometric figures without the benefit of measuring tools. Generally, only a pencil, straightedge, and compass are used.
Distance
The length of the segment between two points
Irrational number
A number that cannot be expressed as a terminating or repeating decimal.
Midpoint
The point on a segment exactly halfway between the endpoints of the segment.
Segment bisector
A segment, line, or plane that intersects a segment at its midpoint.