A quadrilateral is a polygon with four sides and four vertices. If there are two sides intersecting each other, the quadrilateral is a complex polygon. However, most of types of quadrilateral have non-intersecting sides.

A parallelogram is a quadrilateral whose opposite sides are parallel and equal. The opposite angles of a parallelogram are also equal.

A rectangle is a quadrilateral with four right angles. Its' a special case of parallelograms whose opposite sides are parallel and equal.

A square is a special case of rectangle that has four equal sides.

A rhombus is a special case of a parallelogram that has four equal sides. The difference between a square and rhombus is that all angles of a square are right angles, but the angles of a rhombus must not be right angles.

A trapezoid is quadrilateral with one pair of parallel sides. If two pairs of sides are parallel, it is a parallelogram. If the other pair of sides are in equal measure, it is an isosceles trapezoid. If one of sides is perpendicular to the parallel sides, it is a right trapezoid.

A kite is a type of quadrilateral that has two pairs of equal adjacent sides. If all sides are equal, it becomes a rhombus. From this perspective, rhombus is a special case of kit that has all equal sides. One of properties of kit is that two diagonals of a kite are perpendicular.

A dart is also a type of quadrilateral that has two pairs of equal adjacent sides. But the vertex of one pair of equal sides moves inward, which makes it concave.

An antiparallelogram is a type of complex quadrilateral whose two opposite pairs of sides are in equal measure, but the sides in the longer pair intersect each other.

Steven Zheng posted 3 years ago

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