Geometry terms and definitions
To save you having to refer to a dictionary, we’ve listed below some of the more common geometry terms and geometry definitions to help you help with your child’s geometry homework.
Term |
Definition/ Description |
|
| Point | A location in space - a dot on a piece of paper | |
| Line | Connects two points via the shortest path and continues indefintely (forever) in both directions |  |
| Line Segment | Part of a line between two points |  |
| Perpendicular Line Segment | Line Segments that intersect (cross) at an angle of 90° |  |
| Parallel Line Segments | Line segements that never intersect (they are always the same distance apart) |  |
| Right Angle | An angle that measures 90° |  |
| Acute Angle | An angle that measures less than 90° |  |
| Obtuse Angle | An angle that measures more than 90° |  |
| Vertex | Point at which two line segments intersect (forming an angle) |  |
| Scalene Triangle | A triangle with all three sides with different lengths |  |
| Isosceles Triangle | A triangle with two equal length sides (and two equal internal angles) |  |
| Equilateral Triangle | A traingle with all three sides of equal length (each internal angles = 60°) |  |
| Radius | Distance (line segment) from center of a circle to any point on that circle's circumference. |  |
| Diameter | A line segment (or length) joining two points on a circles circumference and passes through the circle's center (twice the length of the radius) |  |
| Circumference | Distance around a circle (the perimeter) | |
| Chord | A line segment joining two points on a curve. |  |
| Arc | Part of a curve |  |
This Math Open Reference Project provides additional information with more geometry terms and definitions.