front 1 point  back 1 an exact position often marked as a dot 
front 2 line  back 2 a straight path of points that is endless in two directions 
front 3 line segment  back 3 a part of a line with two endpoints 
front 4 intersecting lines  back 4 lines that cross at one point 
front 5 parallel lines  back 5 lines that never cross 
front 6 ray  back 6 a part of a line that has one endpoint and continues endlessly in one direction 
front 7 angle  back 7 a figure formed by two rays that have the same endpoint. 
front 8 vertex plural: vertices  back 8 1. the point where two rays met to form an angle.

front 9 right angle  back 9 an angle that forms one square corner or 90 degree angle 
front 10 acute angle  back 10 an angle that's open end measures less than a right angle 
front 11 obtuse angle  back 11 an angle that's open measures more than a right angle 
front 12 perpendicular  back 12 two lines, line segments or rays that form right angles 
front 13 polygon  back 13 a closed figure made up of line segments 
front 14 side  back 14 a line segment forming part of a polygon 
front 15 triangle  back 15 a polygon with 3 sides and 3 vertices 
front 16 quadrilateral  back 16 a polygon with 4 sides and 4 vertices 
front 17 pentagon  back 17 a polygon with 5 sides and 5 vertices 
front 18 hexagon  back 18 a polygon with 6 sides and 6 vertices 
front 19 octagon  back 19 a polygon with 8 sides and 8 vertices 
front 20 decagon  back 20 a polygon with 10 sides and 10 vertices 
front 21 equilateral triangle  back 21 a triangle with all sides the same length 
front 22 isosceles triangle  back 22 a triangle with at least two sides the same length 
front 23 scalene triangle  back 23 a triangle with no sides the same length 
front 24 right triangle  back 24 a triangle with one right angle 
front 25 acute triangle  back 25 a triangle with 3 acute angles 
front 26 obtuse triangle  back 26 a triangle with one obtuse angle 
front 27 trapezoid  back 27 a quadrilateral with only one pair of parallel sides 
front 28 parallelogram  back 28 a quadrilateral in which opposite sides are parallel 
front 29 rectangle  back 29 a quadrilateral with four right angles. It is a special parallelogram 
front 30 rhombus  back 30 a quadrilateral with opposite sides parallel and all sides the same length. Opposite angles are obtuse and the other opposite angles are acute. It is a special parallelogram 
front 31 square  back 31 a quadrilateral with 4 right angles and all sides the same length. it is a special parallelogram and a combination of a rectangle and rhombus 
front 32 diagonal  back 32 a line segment other that a side that connects two vertices of a polygon 