1. Adjacent Angle - Angles in the same plane that have a common vertex and a common side, but no common interior point.

2. Circumference - The distance around a circle.

3. Complementary Angle - Two angles whose sum is 90 degrees.

4. Congruent - Having the same size, shape and angle measurements.

5. Cross-section - A plane figure obtained by slicing a solid with a plane.

6. Irregular polygon - A polygon with sides not equal and/or angles not equal.

7. Parallel lines - Two lines are parallel if they lie in the same plane and they do not intersect.

8. Pi - The relationship of a circle's circumference to its diameter. Pi is typically denoted as 3.14 or 3 1/7.

9. Regular polygon - A polygon with all sides equal and all angels equal.

10. Supplementary angle - Two angles whose sum is 180 degrees.

11. Vertical angles - Two nonadjacent angles formed by intersecting lines or segments. Also called opposite angles.

2. Circumference - The distance around a circle.

3. Complementary Angle - Two angles whose sum is 90 degrees.

4. Congruent - Having the same size, shape and angle measurements.

5. Cross-section - A plane figure obtained by slicing a solid with a plane.

6. Irregular polygon - A polygon with sides not equal and/or angles not equal.

7. Parallel lines - Two lines are parallel if they lie in the same plane and they do not intersect.

8. Pi - The relationship of a circle's circumference to its diameter. Pi is typically denoted as 3.14 or 3 1/7.

9. Regular polygon - A polygon with all sides equal and all angels equal.

10. Supplementary angle - Two angles whose sum is 180 degrees.

11. Vertical angles - Two nonadjacent angles formed by intersecting lines or segments. Also called opposite angles.