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## Lines

point - an exact spot

line - always straight, endless in two directions
ray - part of a line, has one endpoint, endless in one direction
angle - two rays with the same endpoint
right angle - an angle that makes a square corner, sometimes shown with a square in the corner

obtuse angle - an angle that is more than or greater than a right angle, sometimes shown with a curve in the corner

acute angle - an angle that is less than or smaller than a right angle, sometimes shown with a curve in the corner
intersecting lines - lines that cross

## Shapes

polygon - an enclosed shape made with only straight lines

triangle - a polygon with 3 sides
quadrilateral - a polygon with 4 sides
pentagon - a polygon with 5 sides
hexagon - a polygon with 6 sides
octagon - a polygon with 8 sides

## Triangles

acute triangle - any triangle that has 3 acute angles
obtuse triangle - any triangle that has 1 obtuse angle and 2 acute angles
right triangle - any triangle that has 1 right angle and 2 acute angles
equilateral triangle - a triangle with 3 equal sides
isosceles triangle - a triangle with 2 equal sides
scalene triangle - all sides are different lengths

trapezoid - a quadrilateral with exactly one pair of parallel sides

parallelogram - a quadrilateral with exactly two pairs of parallel sides

rectangle - a parallelogram with 4 right angles

rhombus - a parallelogram with 4 equal sides

square - a parallelogram with 4 right angles and 4 equal sides, a rectangle that is also a rhombus