Ginger Sheets, Texhoma High School
Geometry Vocabulary Words
1. Acute Angle is an angle whose measure is between 0 and 90.
2. Acute Triangle has 3 acute angles.
3. Adjacent Angles are two coplanar angles that have a common side and a common
vertex.
4. Adjacent Arcs are on the same circle and have exactly one point in common.
5. Alternate interior angles are nonadjacent interior angles that lie on opposite sides
of the transversal.
6. An altitude of a triangle is a perpendicular segment from a vertex to the line
containing the side opposite that vertex.
7. A biconditional statement is the combination of a conditional statement and its
converse. A biconditional contains the words “if and only if.”
8. A central angle of a circle is an angle whose vertex is the center of the circle.
9. An angle is formed by two rays with the same endpoint. The rays are the sides of
the angle and the common endpoint is the vertex of the angle.
10. An angle bisector is a ray that divides and angle into two congruent angles.
11. The length of an arc of a circle is the product of the ratio measure of arc over 360
and the circumference of the circle.
12. The area of a plane figure is the number of square units enclosed by the figure. A
list of area formulas is on.
13. A central angle of a regular polygon is an angle formed by two consecutive radii.
14. The centroid of a triangle is the point of intersection of the medians of the circle.
15. A chord of a circle is a segment whose endpoints are on the circle.
16. A cicumcenteris the point of curcurrency of the perpendicular bisectors of a
triangle.
17. The circumference of a circle is the distance around the circle. C=pi x d or 2 x pi
x r.
18. Collinear points are points which lie on the same line.
19. A compass is a geometric tool used to draw circles and parts of circles, called
arcs.
20. Complementary angles are two adjacent angles whose sum is 90.
21. Congruent angles are angles that have the same measure.
22. Congruent arcs are arcs that have the same measure and are in the same circle or
congruent circles.
23. Congruent circles are circles whose radii are congruent.
24. A conjecture is a conclusion reached by using inductive reasoning.
25. Consecutive angles share a common side.
26. The conclusion is the then part of an if – then statement.
27. Concurrent lines are three or more lines that meet in one point.
28. A conditional is an if – then statement.
29. A construction is a geometric made with only a straightedge and compass.
30. A contrapositive of a conditional negates both the if and then parts. (If not p, then
not q).
31. The converse of the conditional switches the if and the then parts. (If q, then p)
32. Coplanar figures are figures in the same plane.
33. A corollary is a statement that follows directly from a theorem.
34. Corresponding angles is angle skip angle.
35. A counterexample proves a statement false.
36. CPCTC stands for corresponding parts of congruent triangles are congruent.
37. A dodecagon is a polygon with twelve sides.
38. A cube is a polyhedron with six faces, each of which is a square.
39. A decagon is a polygon with ten sides.
40. Deductive reasoning is a process of reasoning logically from given facts to a
conclusion.
41. An exterior angle of a polygon is an angle formed by a side and an extension of
an adjacent side.
42. A foundation drawing shows the base of a structure and the height of each part.
43. A heptagon is a polygon with seven sides.
44. A hexagon is a polygon with six sides.
45. The hypothesis is the if part of an if-then statement.
46. The incenter of a triangle is the point of concurrency of the angle bisectors of the
triangle.
47. A glide reflection is the composition of a translation followed by a reflection.
48. An inscribed angle in a circle where the vertex of the angle is on the circle and the
sides of the angle are chords of the circle.
49. An intercepted arc is an arc of a circle having endpoints on the sides of an
inscribed angle.
50. An isometric drawing of a three-dimensional object shows a corner view of a
figure.
51. A major arc is an arc that is larger than a semi circle.
52. The measure of an angle is a number of degrees greater than zero and less than or
equal to 180.
53. A median of the triangle is a segment that has as its endpoints a vertex of the
triangle and the midpoint of the opposite side.
54. A midpoint of a segment is the point that divides the segment into two congruent
segments.
55. A kite is a quadrilateral with two pairs of congruent adjacent sides and no
opposite sides congruent.
56. A locus is a set of points, all of which meet a stated condition.
57. A minor arc is an arc that is smaller than a semicircle.
58. A negation of a statement has the opposite meaning of the original statement.
59. A net is a two-dimensional pattern that you can fold to form a three-dimensional
figure.
60. A nonagon is a polygon with nine sides.
61. An obtuse angle is an angle whose measure is between 90 and 180.
62. An obtuse triangle has one obtuse angle.
63. An octagon is a polygon with eight sides.
64. Opposite sides are collinear rays with the same end point. They form a line.
The perpendicular bisector of a segment is a line, segment, or a ray that is
perpendicular to the segment at its midpoint.
65. Perpendicular lines are lines that intersect and form right angles.
66. Pi is the ratio of the circumference of any circle to its diameter.
67. A point is a location that has no size.
68. An orthographic drawing is the top view, front view, and right side view of a
three-dimensional figure.
69. Two lines are parallel if they lie in the same plane and do not intersect.
70. A parallelogram is a quadrilateral with two pairs of parallel sides.
71. Parallel planes are planes that do not intersect.
72. A pentagon is a polygon with five sides.
73. A polygon is a simple, closed, flat figure with at least three sides that are
segments.
74. A ray is a part of a line consisting of one endpoint and all the points of the line on
one side of the endpoint.
75. A rectangle is a parallelogram with four right angles.
76. A quadrilateral is a polygon with four sides.
77. A regular polygon is a polygon that is both equilateral and equiangular.
78. Remote interior angles are the two nonadjacent interior angles corresponding to
each exterior angle of a triangle.
79. A rhombus is a parallelogram with four congruent sides.
80. A right angle is an angle whose measure is 90.
81. A right triangle contains one right angle.
82. Similar polygons are polygons having corresponding angles congruent and
corresponding sides proportional.
83. A sector of a circle is the region bounded by two radii and their intercepted arc.
84. A segment is the part of a line consisting of two points, called endpoints, and all
points between them.
85. A segment bisector is a line, segment, ray, or a plane that intersects a segment at
its midpoint.
86. Skew lines are lines that are neither parallel nor intersecting.
87. Space is the set of all points.
88. A straight angle is an angle whose measure is 180.
89. Two angles are supplementary if the sum of their measures is 180.
90. A theorem is a conjecture that is proven.
91. A transformation is a change in the position, size, or shape of a geometric figure.
92. A translation is a slide.
93. A transversal is a line that intersects two coplanar lines in two points.
94. A figure has symmetry if there is an isometry that maps the figure onto itself.
95. A triangle is a polygon with three sides.
96. A trapezoid is a quadrilateral with exactly one pair of parallel sides, the bases.
97. The truth value of a statement is true or false according to whether the statement
is true or false, respectively.
98. A vector is any quantity that has size and direction.
99. Vertical angles are opposite angles which are congruent.
100.Volume is the measure of the space a figure occupies.