Vocabulary for Unit 5: Geometry
1. line-
a straight path extending in both directions with no endpoints
2. line segment- a part of a line with two endpoints
3. ray-
a part of a line that has one endpoint and continues
without end in one direction
4. parallel lines- lines that never intersect and are always the same distance
apart
5. perpendicular lines- two lines, segments, or rays that intersect to form right
angles
6. polygon-
a closed 2-dimensional figure with 3 or more sides
7. regular polygon- polygon that has all sides congruent and all angles
congruent
8. acute angle- an angle with a measure less than 90 degrees
9. right angle- an angle that measures exactly 90 degrees
10. obtuse angle- an angle with a measure more than 90 degrees
11. straight angle- an angle with a measure of 180 degrees
12. triangle-
a polygon with 3 sides
13. acute triangle- a triangle with all acute angles
14. right triangle- a triangle that has a 90 degree angle
15. obtuse triangle- a triangle that has an obtuse angle
16. equilateral triangle- a triangle with all equal sides
17. isosceles triangle- a triangle with two equal sides
18. scalene triangle- a triangle with no equal sides
19. quadrilateral- a polygon with 4 sides
20. square-
a quadrilateral with equal sides and four 90 degree angles
21. rectangle-
a quadrilateral with two pairs of equal and parallel sides with
four 90 degree angles
22. parallelogram- a quadrilateral whose opposite sides are parallel and
congruent
23. rhombus-
a parallelogram with four equal sides
24. trapezoid-
a quadrilateral with exactly one pair of parallel sides
25. pentagon-
a polygon with 5 sides
26. hexagon-
a polygon with 6 sides
27. octagon-
a polygon with 8 sides
28. line of symmetry- a line that divides a figure into two halves that a mirror
images of each other
29. perimeter- the distance around a figure
30. area-
the measure, in square units, of the inside of a plane figure (flat
surface)
31. congruent- having the same size and shape; including the sides and
angles
32. similar-
polygons that have the same shape, but not necessarily the
same size; angles are the same, but sides are different