Question | Answer |
acute angle | an angle with a measure between 0 and 90 degrees |
acute triangle | a triangle with three acute angles |
adjacent angles | two angles that have the same vertex and a common side, but no common interior points |
altitude of a triangle | a segment from a vertex of a triangle that is perpendicular to a line containing the opposite side of the triangle |
angle bisector | the ray in the interior of an angle that divides the angle into two congruent angles |
angle | the figure formed by two rays with a common endpoint |
bisector of a segment | any point, segment, ray, or line that cuts the segment in half. |
center of a circle | the point that is equidistant from every point on the circle |
chord of a circle | a segment whose endpoints are on the circle |
circle | the set of all points in a plane that are the same distance from a given point |
closed curve | a path in a plane that begins and ends at the same point |
collinear | points that lie on the same straight line |
complementary angles | two angles whose measures have a sum of 90 degrees |
concave polygon | a polygon in which one or more of the interior angles is greater than 180 degrees |
concurrent lines | three or more lines that intersect in one point |
congruent segments | segments that have the same length |
coplanar | points that lie on the same plane |
decagon | a polygon having ten sides |
degree measure | a number which describes the size of an angle |
diameter of a circle | a chord that goes through the center of the circle |
dodecagon | a polygon having twelve sides |
equiangular triangle | a triangle with three congruent angles |
equilateral triangle | a triangle with three congruent sides |
exterior of an angle | the set of all points not in the interior or on the angle |
heptagon | a polygon having seven sides |
hexagon | a polygon having six sides |
interior angle of a polygon | an angle formed by two sides of the polygon that have the same endpoint |
interior of an angle | the set of all points contained on and inside the two rays of an angle |
isosceles triangle | a triangle with at least two congruent sides |
kite | a quadrilateral having two pairs of adjacent sides that are congruent (no side is used twice in the pairs) |
length measure | a number assigned to a segment to describe its length |
line | a set of points in a straight, unlimited length, with no thickness or endpoints |
linear pair of angles | two adjacent angles whose noncommon sides are on the same line |
median of a triangle | a segment from the vertex of an interior angle to the midpoint of the opposite side |
midpoint of a segment | the point on a segment which divides the segment in half |
n-gon | a polygon with a whole number 'n' number of sides |
nonagon | a polygon having nine sides |
nonsimple closed curve | a closed curve that crosses itself at least once |
nonsimple polygon | a polygon with at least one pair of segments that intersect at a point that is not their endpoint |
obtuse angle | an angle with a measure between 90 and 180 degrees |
obtuse triangle | a triangle with one obtuse angle |
octagon | a polygon having eight sides |
parallel lines | two or more lines that are always the same distance apart |
parallelogram | a quadrilateral with opposite sides parallel and congruent |
pentagon | a polygon having five sides |
perpendicular bisector | a line perpendicular to a segment that divides the segment into two congruent segments |
perpendicular lines | two lines which intersect to form four right angles |
plane | a set of points in a flat surface that has no thickness and no edges |
point of intersection | the point where two or more lines cross each other |
point | a location that has no length, width or thickness |
polygon | a shape formed by three or more points joined by three or more straight lines. |
protractor | a device for measuring angles |
quadrilateral | a polygon having four sides |
radius of a circle | a segment whose endpoints are the center of the circle and a point on the circle |
ray | A part of a line extending in one direction from one endpoint though another point. |
rectangle | a quadrilateral in which opposite sides are congruent and parallel and all interior angles are right angles |
reflex angle | an angle that is greater than 180 degrees but less than 360 degrees |
regular polygon | a simple polygon with all sides congruent and all interior angles congruent |
rhombus | a quadrilateral having four congruent sides and opposite sides parallel |
right angle | an angle with a measure of 90 degrees |
right triangle | a triangle with one right angle |
scalene triangle | a triangle with no congruent sides |
segment | the part of a line between two endpoints |
sides of the triangle | the three line segments which meet each other only at their end points |
simple closed curve | a closed curve that does not cross itself |
simple convex polygon | a polygon where all interior angles are less than 180 degrees. |
simple nonconvex polygon | a concave polygon |
simple polygon | a polygon with all its segments touching only at their endpoints |
skew lines | Nonintersecting lines that do not lie in the same plane |
space | the set of all points that has no boundaries |
square | a quadrilateral having four congruent sides and four right angles |
straight angle | an angle that measures 180 degrees |
supplementary angles | two angles whose measures have a sum of 180 degrees |
trapezoid | a quadrilateral having only one pair of opposite sides parallel |
triangle | a polygon having three sides |
vertex of an angle | the common end point of the two rays that form the angle |
vertices of a triangle | the three endpoints of the sides of the triangle |
vertical angles | two angles that are formed by intersecting lines that are not a linear pair of angles |
zero angle | an angle with no rotation (actually a ray) |
icosagon | a polygon with twenty sides |