Introduction to Geometry - Figures
Decagon
A ten sided polygon.
right angle
A 90 degree angle
polygon
A closed plane figure made up of line segments
rectangle
A parallelogram with 4 right angles
parallelogram
A quadrilateral with two pairs of parallel sides
acute angle
An angle less than 90 degrees
obtuse angle
An angle more than 90 degrees
Octagon
An eight sided polygon.
plane
a flat surface that continues forever
diagonal
a line segment connecting any two vertices of a polygon
rhombus
a parallelogram with 4 congruent sides
square
a parallelogram with four congruent sides and four right angles
equilateral polygon
a polygon in which all sides are congruent
convex polygon
a polygon in which each of its diagonals are inside the polygon
regular polygon
a polygon with all sides and all angles equal
concave polygon
a polygon with at least one diagonal outside the polygon
pentagon
a polygon with five sides
quadrilateral
a polygon with four sides
hexagon
a polygon with six sides
triangle
a polygon with three sides
kite
a quadrilateral with two pairs of congruent sides
bisector
a ray, line, line segment, or plane that intersects the segment at its midpoint, a line, ray, segment, or plane that intersects a segment at its midpoint
obtuse triangle
a triangle with an obtuse angle
scalene triangle
a triangle with no two sides of equal length
right triangle
a triangle with one right angle
acute triangle
a triangle with three acute angles
equilateral triangle
a triangle with three congruent sides
isosceles triangle
a triangle with two equal sides
line
defined as having infinite length, but no width or thickness
angle
formed by two rays that share a common endpoint
ray
part of a line with one endpoint
line segment
part of a line with two endpoints