1. Points, Lines, and Shapes!
Geometry
Points, Lines, and Shapes!

2. Plane
plane A flat surface that stretches into infinity.

3. Point
point A location in a plane or in space, having no dimensions.

4. Line Segment
line segment Two points on a line, and all the points between those two points.

5. Line
line A straight set of points that extends into infinity in both directions.

6. Ray
ray part of a line, with one endpoint, and extending to infinity in one direction.

7. Intersecting Lines
intersecting lines Lines that have one and only one point in common.

8. Parallel Lines
parallel lines Two lines are parallel if they are in the same plane and never intersect.

9. Perpendicular Lines
perpendicular lines Two lines are perpendicular if the angle between them is 90 degrees.

10. Angle
angle The union of two rays with a common endpoint, called the vertex.

11. Acute Angle
acute angle A positive angle measuring less than 90 degrees.

12. Right Angle
right angle An angle whose measure is 90 degrees.

13. Obtuse Angle
obtuse angle An angle whose measure is greater than 90 degrees.

14. Straight Angle
straight angle An angle that measures 180 degrees.

15. Polygon
polygon A closed plane figure made up of several line segments that are joined together.

16. Triangle triangle A three-sided polygon.
Triangles can be classified according to the measures of their angles and their sides.

17. Acute Triangle
acute triangle A triangle each of whose angles measures less than 90 degrees.

18. Right Triangle
right triangle A triangle that contains a right angle.

19. Obtuse Triangle
obtuse triangle A triangle with an obtuse angle.

20. Scalene Triangle
scalene triangle A triangle with no congruent (exactly the same size and shape) sides.

21. Isosceles Triangle
isosceles triangle A triangle with two congruent (exactly the same size and shape) sides.

22. Equilateral Triangle
equilateral triangle A triangle with all sides that are congruent (exactly the same size and shape).

23. Circle
circle The set of points in a plane that are a fixed distance from a given point, called the center.

24. Circle
circle The set of points in a plane that are a fixed distance from a given point, called the center.

25. Quadrilateral
quadrilateral Any four-sided figure is called a quadrilateral.

26. Parallelogram
parallelogram A quadrilateral with opposite sides parallel.

27. Rectangle
rectangle A parallelogram with four 90-degree (right) angles.

28. Square
square A parallelogram with four congruent (equal) sides and four 90 degree (right) angles.

29. Rhombus rhombus A parallelogram with four congruent (equal) sides.
Opposite angles are congruent.

30. Trapezoid
trapezoid A quadrilateral that has exactly one pair of parallel sides.
The parallel sides are called bases.
The non-parallel sides are called legs.
If the legs have the same length, then the trapezoid is an isosceles trapezoid.
Isosceles Trapezoid
Isosceles Trapezoid

31. Kite
kite A quadrilateral that is shaped like a diamond. Sometimes people like to fly them! 
It has two distinct pairs of adjacent (side-by-side) congruent sides.

32. Cylinder
cylinder a solid figure that has two parallel bases that are congruent circles

33. Cone
cone a solid figure that has a flat, circular base and one vertex

34. Cube
cube a solid figure with six congruent square faces

35. Square Pyramid
Square Pyramid a solid figure with a square base and with four triangular faces that have a common point

36. Rectangular Prism
Rectangular Prism a solid figure in which all six faces are rectangles.

37. Rotation (turn)
Rotation (turn) a movement of a figure to a new position by turning it around a vertex

38. Reflection (flip)
Reflection (flip) a movement of a figure to a new position by flipping it over a line

39. Translation (slide)
Translation (slide) a movement of a figure to a new position along a straight line