Go to my LINKS page and check out the Geometry
vocabulary site. Students must memorize
all 42 terms.
Geometry Vocabulary
1. plane figure - a figure that lies on a plane;
flat
2. 1 dimensional figure - an object measured in 1
direction (length)
3. line segment - a part of a line with 2 endpoints
4. line - a straight path on a plane, that goes on
and on in 2 directions
5. ray - a part of a line with an endpoint that
goes on and on in 1 direction
6. right angle - measures exactly 90 degrees; a
“perfect” corner
7. acute angle - smaller than a right angle (“a
cute little angle”)
8. obtuse angle - larger or open wider than a right
angle
9. parallel lines - 2 lines that are the same
distance apart, that will never meet
10. intersecting lines - lines that cross or meet
at exactly 1 point
11. perpendicular lines - lines that cross or meet
to form right angles
12. 2 dimensional figure - an object measured in 2
directions, by length and width
13. vertex/vertices - the point where 2 line segments meet in 2D objects, or
where 3 faces meet in 3D objects
14. polygon - a closed plane (flat) figure with
straight sides
15. circle - a curved plane figure with each point
on the curved line being the same distance from its center point
16. triangle - a polygon with 3 sides, angles, and
vertices
17. quadrilateral - any polygon with 4 sides and 4
angles; There are 6 types: square, rectangle, parallelogram, rhombus,
trapezoid, and a general quadrilateral
18. square - a polygon with 4 congruent sides and 4
right angles; its opposite sides are parallel and congruent
19. rectangle - a polygon with 4 right angles,
whose opposite sides are parallel and congruent
20. pentagon - a polygon with 5 sides, angles, and
vertices
21. hexagon - a polygon with 6 sides, angles, and
vertices
22. octagon - a polygon with 8 sides, angles and
vertices
23. decagon - a polygon with 10 sides, angles and
vertices
24. parallelogram - a polygon whose opposite sides
are parallel and congruent (2 pairs of parallel sides)
25. rhombus - a parallelogram whose 4 sides and
opposite angles are congruent
26. trapezoid -a quadrilateral with only 1 pair of
parallel sides
27. symmetry/lines of symmetry - a figure has line
symmetry if it can be folded where the one half is an exact fit on top of the
other; a square has 4 lines of symmetry
28. congruent - same size and shape
29. transformation - the movement of any shape in
geometry; 3 types: reflection, translation, rotation
30. reflection - when 1 shape makes the mirror
image of another shape; flip
31. translation - when 1 shape slides into another
position; slide
32. rotation - when 1 shape turns around a point;
turn
33. 3 dimensional figure - measured in 3
directions: length, width, and height
34. face - the flat surfaces that makes up a 3D
figure
35. edge - the line segment where 2 faces meet
36. sphere - a 3D object with 1 curved surface
37. cube or square prism - a 3D object with 6
congruent square faces
38. rectangular prism - a 3D object with 6
rectangular faces
39. triangular prism - a 3D object with 2
triangular and 3 rect. faces
40. pyramid - ”spear-a-mid” 3 types: square,
rectangular, triangular; it is named by its 2 bases
41. cylinder - has 2 flat circular faces and 1
curved surface; examples: tissue rolls, cans
42. cone - has 1 flat circular face and 1 curved
surface; examples: party hats, ice cream cones