Geometry

4. A flat, two-dimensional surface extending infinitely in all directions.
7. The measure of space inside a two-dimensional shape.
8. A proven statement or proposition in geometry.
10. A segment connecting the midpoints of two sides of a triangle.
12. An exact location in space with no size, only position.
14. A line that intersects two or more lines at distinct points.
16. A part of a line that starts at a point and extends infinitely in one direction.
19. A six-sided polygon.
20. The total length of the sides of a two-dimensional shape.
21. The point where the three altitudes of a triangle intersect.

1. The statement formed by negating both the hypothesis and conclusion of a conditional statement.
2. The statement formed by exchanging the hypothesis and conclusion of a conditional statement.
3. Relating to a line or straight path.
5. Lines or segments that intersect to form right angles.
6. A line segment drawn from a vertex of a triangle to the midpoint of the opposite side.
7. A line from the center of a regular polygon perpendicular to one of its sides.
9. A seven-sided polygon.
11. The quality of two figures being similar in shape but different in size.
13. The distance around the edge of a circle.
15. A ten-sided polygon.
17. A twelve-sided polygon.
18. The exact middle point of a line segment.