Basic Geometry ConceptsSome basic geometry concepts, words and notations that you would need to know are points, lines, line segments, midpoints, rays, planes and space.
PointsWe may think of a point as a "dot" on a piece of paper or the pinpoint on a board. In geometry we usually identify this point with a number or letter. A point has no length, width, or height - it just specifies an exact location. It is zero-dimensional. The following is a diagram of points A, B, and M: LinesA line is one-dimensional. That is, a line has length, but no width or height. In geometry, a line extends forever in both directions. A line is uniquely determined by two points.
Line segmentsA line segment connects two endpoints. A line
segment with two endpoints A and B is denoted by
A line segment can also be drawn as part of a line.
Midpoint The midpoint of a segment divides the segment into two segments
of equal length. The diagram below shows the midpoint M of
the line segment RaysA ray starts from one endpoint and extends forever in one direction.
PlanesPlanes are two-dimensional. A plane has length and width, but no height, and extends infinitely on all sides. Planes are thought of as flat surfaces, like a tabletop. A plane is made up of an infinite amount of lines. Two-dimensional figures are called plane figures.
SpaceSpace is the set of all points in the three dimensions - length, width and height. It is made up of an infinite number of planes. Figures in space are called solids.
VideosThe following video gives the definitions of a point, a line, a plane, and space, as well as the symbols that are used in Geometry to represent each figure.
General Angle Basics: Angle Characteristics - rays, vertex,
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