1.
A angle: A figure formed by two rays that begin at the same point
2.
A line: Straight path that extends forever in both directions
3.
A plane: Flat surface extending forever in all directions
4.
A point: Exact location in space
5.
Acute angle: Angle less than 90 degrees
6.
Acute triangle: Less than 90 degrees
7.
Complementary angles: Angles that add up to 90
8.
Congruent figures: Figures that are the same size and same shape
9.
Decagon: Polygon with ten sides
10.
Diagonal: A line segment that joins two vertices of a polygon but it not a side
11.
Equilateral triangle: Three sides that have the same length
12.
Heptagon: Polygon with seven sides
13.
Hexagon: Polygon with six sides
14.
Intersecting Lines: A straight path that has one end point and extends forever in the opposite direction
15.
Isosceles triangle: Two sides that have the same length
16.
Line of symmetry: Place where a figure can be folded so that both halves are congruent
17.
Line segment: Straight path between two endpoints
18.
Nonagon: Polygon with nine sides
19.
Obtuse angle: Greater than 90 degrees and less than 180 degrees
20.
Obtuse triangle: Greater than 90 degrees
21.
Octagon: Polygon with eight sides
22.
Parallel lines: Lines that do not cross
23.
Parallelogram: Opposite sides parallel, opposite sides congruent
24.
Pentagon: Polygon with five sides
25.
Perpendicular lines: Lines that cross at 90 degree angle
26.
Polygon: Closed figure formed by line segments joined only a their endpoints
27.
Rectangle: Parallelogram, 4 right angles
28.
Reflection: A flip
29.
Regular polygon: All sides congruent and all angles congruent
30.
Rhombus: Parallelogram, 4 congruent sides
31.
Right angle: Angle that is 90 degrees
32.
Right triangle: 90 degrees angle
33.
Rotation: A turn
34.
Scalene triangle: No sides that have the same length
35.
Similar figures: Figures that are the same shape and may or may not have the same size
36.
Square: Parallelogram, 4 right angles, 4 congruent sides
37.
Supplementary angles: Angles that add up to 180
38.
Transformation: The movement of a geometric figure
39.
Translation: A slide
40.
Trapezoid: One pair of opposite sides parallel
41.
Vertex: End point