| A | B |
|---|
| acute angle | An angle whose measure is greater than 0 and less than 90 |
| acute triangle | A triangle in which all three angles are acute |
| altitude (of triangle) | A perpendicular segment from a vertex of a triangle to the opposite side |
| angle | A figure formed by two rays with a common endpoint |
| annulus | A region bounded by two concentric circles |
| apothem | A segment joining the center of a regular polygon to the midpoint of one of the polygon's sides |
| arc | A figure consisting of two points on a circle and all the points on the circle needed to connect them by a single path |
| area | The number of square units of space within the boundary of a closed region |
| mean | The average of a set of numbers |
| bisect | To divide a segment or angle into two congruent parts |
| central angle | An angle whose vertex is at the center of a circle |
| chord | A segment joining two points on a circle |
| circumference | The perimeter of a circle |
| circumscribed polygon | A polygon each of whose sides is tangent to a circle |
| collinear | Lying on the same line |
| complementary angles | Two angles whose sum is 90 degrees |
| concentric circles | Two or more coplanar circles with the same center |
| concurrent lines | Lines that intersect in a single point |
| conditional statement | A statement in the form "If p, then q," where p and q are declarative statements |
| congruent | Equal |
| contrapositive | A statement associated with a conditional statement "If p, then q," having the form "If not q, then not p." |
| converse | A statement associated with a conditional statement "If p then q," having the form "If q, then p." |
| convex polygon | A polygon in which each interior angle has a measure less than 180 |
| coplanar | Lying in the same plane |
| cross section | The intersection of a solid with a plane |
| cyclic quadrilateral | A quadrilateral that can be inscribed in a circle |
| diagonal | A segment that joins two nonconsecutive vertices of a polygon |
| diameter | A chord that passes through the center of the circle |
| equiangular | Having all angles congruent |
| equilateral | Having all sides congruent |
| face | One of the polygon surfaces |
| foot (of line) | The point of intersection of a line and a plane |
| frustrum | The portion of a pyramid or a cone that lies between the base and a cross section of the figure |
| hypotenuse | The side opposite the right angle in a right triangle |
| hypothesis | The "if" clause in a conditional statement |
| inscribed angle | An angle whose vertex is on a circle and whose sides are determined by two chords |
| inscribed polygon | A polygon each of whose vertices lies on a circle |
| inverse | A statement associated with a conditional statement "If p, then q," having the form "If not p, then not q" |
| isosoles trapezoid | A trapezoid in which the nonparallel sides are congruent |
| isosoles triangle | A triangle in which at least two sides are congruent |
| kite | A qudrilateral in which two disjoint pairs of cosecutive sides are congruent |
| locus | A set consisting of all the points, and only the points, that satisfy specific coditions |
| median (of trapezoid) | A segment joining the midpoints of the nonparallel sides of a trapezoid |
| median (of triangle) | A segment from a vertex of a triangle to the midpoint of the opposite side |
| midpoint | A point that divides a segment or an arc into two congruent parts |
| oblique lines | Two intersecting lines that are not perpendicular |
| obtuse angle | A angle whose measure is greater than 90 and less than 180 |
| obtuse triangle | A triangle in which one of the angles is obtuse |
| opposite rays | Two collinear rays that have a common endpoint and extend in opposite directions |
| parallel lines | Coplanar lines that do not intersect |
| parallelogram | A quadrilateral in which both pairs of opposite sides are parallel |
| perimeter | The sum of the lengths of the sides of a polygon |
| perpendicular | Intersecting at right angles |
| perpendicular bisector | A line that bisects and is perpendicular to a segment |
| postulate | An unproved assumption |
| proportion | An equation stating that two or more ratios are equal |
| protractor | An instrument, marked in degrees, used to measure angles |
| rate | The relationship of two quantities that have different units of measure |
| ratio | The relationship of two quantities that have the same unit of measure |
| ray | A straight set of points that begins at an endpoint and extends infinitely in one direction |
| right triangle | A triangle in which one of the angles is a right angle |
| scalene triangle | A triangle in which no two sides are congruent |
| secant | A line that intersects a circle at exactly two points |
| sector | A region bounded by two radiiand an arc of a circle |
| similar figures | Figures that have the same shape but not necessarily the same size |
| skew lines | Two lines that are not coplanar |
| slant height | A perpendicular segment from the vertex of a pyramid to a side of the pyramid's base |
| straight angle | An angle whose measure is 180 |
| supplementary angles | Two angles whose sum is 180 |
| tangent | A line that intersects a circle at exactly one point |
| theorem | A mathematical statement that can be proved |
| transversal | A line that intersects two coplanar lines in two distict points |
| trisect | To divide a segment or angle into three congruent parts |
| vertex | The common endpoint of an angle or polygon |
| vertical angles | A pair of angels such that the rays forming the sides of one and the rays forming the sides of the other are opposite rays |
| volume | The number of cubic units of space contained by a solid figure |
