Download Geometry Terms

Geometry Terms
Points and Lines
Point: a location on an object or a position in space
Line: a connected set of points extending forever in both
directions
A line is named by two points on the line.
Examples: ⃡ or ⃡
Line Segment: two points (endpoints) and the straight
path between them
A line is named by its endpoints
Examples: ̅̅̅̅ ̅̅̅̅
Ray: part of a line that extends in one direction and has
one endpoint
A ray is named by its endpoint and another point on the
line. The endpoint is always named first.
Examples:
Parallel: two lines that are always the same distance apart
The symbol for parallel is ǁ
Intersecting: two lines that cross or will cross if extended
Perpendicular: two lines that form right angles when they
intersect (meet)
©Carie Whitehead 2013
carie.whitehead.people.cpcc.edu
Angles
Angle: the distance between two rays
Angles are measured in degrees, related to a circle. A full
circle is 360°
Straight Angle: an angle that forms a straight line and
measures 180°
Acute Angle: an angle that measures less than 90°
Obtuse Angle: angles that measure more than 90° but less
than 180°
Right Angle: an angle that measures exactly 90°
A right angle is ¼ of a circle.
A right angle is identified by the square corner.
©Carie Whitehead 2013
carie.whitehead.people.cpcc.edu
Polygons
Polygon: a plane (flat) figure formed by three or more lines
Regular Polygon: a two-dimensional shape that is closed,
has straight sides, and all of the sides are the same length
Triangles: polygons with three sides and three angles
 Right Triangle: a triangle with one right angle
(90°). The side opposite the right angle is called
the hypotenuse.

Equilateral Triangle: a triangle with three equal
angles (60° each) and three equal sides

Isosceles Triangle: a triangle with two equal
angles. The sides opposite the equal angles are
also equal.

Scalene Triangle: a triangle with no equal sides
and no equal angles.
Quadrilaterals: four-sided polygons
 Parallelogram: a quadrilateral with opposite sides
parallel. Opposite sides and opposite angles are
equal.

Rhombus: a regular parallelogram, all four sides
are equal

Rectangle: a quadrilateral with two pairs of
parallel sides and four right angles. Opposite sides
are of equal length.

Square: a regular rectangle, all four sides are equal

Trapezoid: a quadrilateral with one pair of parallel
sides, called bases. All four sides can be of
different lengths.
Pentagon: a five-sided polygon
Hexagon: a six-sided polygon
Octagon: an eight-sided polygon
©Carie Whitehead 2013
carie.whitehead.people.cpcc.edu