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Geometry is about the shape and size of things. Like algebra, geometry has its own special vocabulary. These pictures show the four basic concepts on which the rest of geometry is built.
Move your mouse cursor over each illustration to learn more.
A part of a line that has two endpoints.
A part of a line that has only one endpoint.
Two rays joined with a common endpoint.
A plane is a flat surface that extends endlessly in all directions. Points that lie on the same plane are called coplanar. Plane geometry deals with two-dimensional figures.
A point is a geometric object that has no dimensions, only a location.
A line is a collection of points along a straight path, having no endpoints. Points that lie on the same line are called collinear.
The set of all points! Space geometry deals with three-dimensional figures
Below are several other important terms.
Click on each to see what it means.
Geometry Building Blocks
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Pairs of lines