A shape is any plane figure with side and/or vertices.
A quadrilateral is a four-sided figure whose internal angles are 360 degrees.
A square is a quadrilateral that has four equal sides and four equal angles. The diagonals of a square bisect each other and the opposite sides of the square are parallel.
A rectangle is a four-sided shape where the opposite sides are parallel and of equal length. The diagonals of the rectangle also bisect each other.
A parallelogram is a quadrilateral where both pairs of opposite sides are equal. Its opposite sides and angles are congruent. Each diagonal of a parallelogram separates into two congruent triangles. A parallelogram is a convex polygon (interior angles less than 180 degrees.)
A rhombus has four equal sides, the diagonals of the square are perpendicular and bisect the opposite angles. Its vertices are not 90 degrees. The rhombus is not a cyclic quadrilateral (vertices lie on a single circle.)
PROPERTIES OF QUADRILATERALS:
1. Opposite sides are equal.
2. Opposite sides are parallel.
3. Opposite angles are equal.
4. Sum of two adjacent angles is 180 degrees.
5. Diagonals bisect each other.
