What is a Rectangle?

E, F, G, and H label the four vertices of the rectangle
The arrows indicate that opposite sides are parallel
The bars over EH, FG, EF, and HG indicate that they are line segments
The equal sign with a squiggly line over it means 'congruent to'
The short black lines crossing through the sides are to show which sides are congruent
The boxes in each corner represent right, or 90^o angles
The small 'o' symbol means 'degrees'
The slanted looking 'L' is the symbol for an angle, and the 'm' means 'measurement'

1. A quadrilateral is just a closed figure with four sides, so every rectangle is a quadrilateral
2. Parallel lines, if extended out forever, will never intersect
3. 'Congruent' means the 'same length'
4. 90-degree angles are also called 'right angles'
1. Note that not every quadrilateral is going to be a rectangle!
2. You could have a four-sided figure whose angles are not right angles, which would not be a rectangle
1. The difference between rectangles and parallelograms is rectangles must have right angles
2. You can have a parallelogram whose angles are not right angles
3. So not all parallelograms are rectangles
4. But all rectangles ARE parallelograms!

What is a rectangle?