A quadrilateral is a polygon which has 4 sides.
There are different kinds of quadrilaterals. Their characteristics enable us to tell them apart.
There are other kinds of quadrilaterals without a specific name. They are called general quadrilaterals.
Examples:
The square is a convex polygon. |  |
It has 2 pairs of parallel sides. |  |
| Its 4 sides are the same length (isometric). |  |
It has 4 right angles. |  |
The rectangle is a convex polygon. |  |
It has 2 pairs of parallel sides. |  |
| Its opposite sides are the same length (isometric). |  |
It has 4 right angles. |  |
The rhombus is a convex polygon. |  |
It has 2 pairs of parallel sides. |  |
| Its 4 sides are the same length (isometric). |  |
| Its opposite angles are congruent (isometric). |  |
The parallelogram is a convex polygon. |  |
It has 2 pairs of parallel sides. |  |
| Its opposite sides are the same length (isometric). |  |
| Its opposite angles are congruent (isometric). |  |
The trapezoid is a convex polygon. |  |
It has 1 pair of parallel sides. |  |