1. Acute Triangle
Definition A triangle that has three acute angles.

2. Right Triangle
Definition A triangle with one right angle.

3. Obtuse Triangle
Definition A triangle with one obtuse angle.

4. Median (in a triangle)
Definition A segment that has its endpoints on a vertex of the triangle and the midpoint of the opposite side.

5. Angle Bisector (in a triangle)
Definition A segment from a vertex to the opposite side that separates the angle into two congruent angles.

6. Altitude (in a triangle)
Definition The perpendicular segment from a vertex of the triangle to the line containing the opposite side.

7. Parallelogram
Definition A quadrilateral with two pairs of parallel sides.

8. Rectangle
Definition An equiangular quadrilateral.

9. Rhombus
Definition An equilateral quadrilateral.

10. Square
Definition A regular quadrilateral.

11. Kite
Definition A quadrilateral with two pairs of consecutive sides that are congruent and no opposite sides congruent.

12. Trapezoid
Definition A quadrilateral with exactly one pair of parallel sides.