31 terms

# Geometry

Geometry vocabulary (common core)
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plane
an endless flat surface
parallel lines
lines that NEVER intersect
intersecting lines
lines that pass through the same point
perpendicular lines
lines that form right angles (perfect square corners; 90 degrees)
line segment
a part of a line with two endpoints
ray
a part of a line that has one endpoint and continues on forever in one direction
right angle
measures 90 degrees; forms a perfect square corner
acute angle
measures less than a right angle
obtuse angle
measures greater than a right angle, but less than a straight angle
straight angle
forms a straight line
polygon
a closed plane figure made up of line segments
side
a line segment of a polygon
vertex
the point where two sides meet on a polygon
triangle
3-sided polygon
4-sided polygon
pentagon
5-sided polygon
hexagon
6-sided polygon
octagon
8-sided polygon
equilateral triangle
has 3 equal sides
isosceles triangle
has 2 equal sides
scalene triangle
no equal sides
right triangle
has 1 right angle
acute triangle
has 3 acute angles
obtuse triangle
has 1 obtuse angle
parallelogram
has 2 pairs of parallel sides
square
*has 4 right angles
*has 2 pairs of parallel sides
*all sides are equal
rectangle
*has 4 right angles
*has 2 pairs of parallel sides
*opposite sides are equal in length
rhombus
*has 2 pairs of parallel sides
*all sides are equal
trapezoid
*has 1 pair of parallel sides
symmetric
when a figure can be folded on a line to form two equal halves that fit on top of each other
line of symmetry
the fold line