apothem - a segment joining the center of a regular polygon to the midpoint of one of the polygon's sides
chord - a segment joining two points on a circle
concave polygon- A polygon that has one or more interior angles greater than 180° (Result: some vertices point 'inwards', towards the the center.) Some of the diagonals of a concave polygon will lie outside the polygon.
convex polygon - A polygon that has all interior angles less than 180° (Result: All the vertices point 'outwards', away from the center.) All of the diagonals of a convex polygon will be inside the polygon.
diagonal (of a polygon) - a segment that joins two nonconsecutive (nonadjacent) vertices of a polygon
equilateral triangle - A triangle with three congruent (equal) sides.
isosceles triangle - A triangle with two congruent (equal) sides.
kite - a quadrilateral in which two disjoint sides are congruent
median (of a trapezoid) - A segment that joins the midpoint of the nonparallel sides of a trapezoid. The length of the median is the average of the two bases (parallel sides).
oblique - not right
parallelogram - A quadrilateral (4-sided polygon) that has two pairs of opposite sides which are parallel.
regular (polygon) - a polygon that is both equilateral and equiangular
rhombus - a parallelogram with four congruent (equal length) sides.
scalene triangle - A triangle that has no sides which are congruent (equal).
trapezoid - a quadrilateral with exactly one pair of parallel sides
chord - a segment joining two points on a circle
concave polygon- A polygon that has one or more interior angles greater than 180° (Result: some vertices point 'inwards', towards the the center.) Some of the diagonals of a concave polygon will lie outside the polygon.
convex polygon - A polygon that has all interior angles less than 180° (Result: All the vertices point 'outwards', away from the center.) All of the diagonals of a convex polygon will be inside the polygon.
diagonal (of a polygon) - a segment that joins two nonconsecutive (nonadjacent) vertices of a polygon
equilateral triangle - A triangle with three congruent (equal) sides.
isosceles triangle - A triangle with two congruent (equal) sides.
kite - a quadrilateral in which two disjoint sides are congruent
median (of a trapezoid) - A segment that joins the midpoint of the nonparallel sides of a trapezoid. The length of the median is the average of the two bases (parallel sides).
oblique - not right
parallelogram - A quadrilateral (4-sided polygon) that has two pairs of opposite sides which are parallel.
regular (polygon) - a polygon that is both equilateral and equiangular
rhombus - a parallelogram with four congruent (equal length) sides.
scalene triangle - A triangle that has no sides which are congruent (equal).
trapezoid - a quadrilateral with exactly one pair of parallel sides