Quadrilateral is a group of geometric shapes, figures or diagrams that have a distinct attribute. There are innumerable geographic shapes or figures and there are endless possibilities of tweaking the conventional diagrams or forms. Almost all such shapes and figures are classified in specific groups based on their similarities. Quadrilateral is one such classification or group.
Quadrilateral Definition
Quadrilateral literally means four sides. Any shape that has four sides will be considered a quadrilateral. The name itself is a coinage of quad and lateral. Quad means four and lateral is side. A quadrilateral is a two dimensional figure. It cannot be three dimensional because then it would not have four sides. Imagine any three dimensional figure and it would have more than four sides or edges. Whenever thickness or depth comes into the picture, there are more edges, sides, angles or vertices. Accordingly, a quadrilateral can be illustrated further.
A quadrilateral should have four sides, four edges, four vertices forming four angles and those interior angles must collectively form 360 degrees. It is a given that the sides would have to be straight lines since the moment you bend the lines beyond a quad shaped figure, you would have more sides unless it is an open shape.
Common Quadrilaterals
There are two types of quadrilaterals, regular and irregular. The common quadrilaterals are square, rectangle, rhombus, trapezoid and kite. Square, rectangle and rhombus qualify as parallelograms. Parallelograms are hence a form of quadrilateral. Only square is a regular quadrilateral because all its four sides are equal. All other shapes listed here are irregular quadrilaterals.
• A rectangle with its four sides, four right angles and parallel opposite sides being equal in length is a parallelogram and a quadrilateral.
• A rhombus, also called a diamond or rhomb, with its four equal sides but not forming right angles is a quadrilateral.
• A trapezoid, also called trapezium, with two equal parallel sides and two unequal parallel sides is a quadrilateral. A trapezoid has two acute angles and two obtuse angles. There are no right angles in a trapezoid. There are many variants of trapeziums, like the isosceles trapezoid.
• The shape of a kite makes it a quadrilateral. There are two equal sides adjacent to one another at the top and the two sides at the bottom are also equal. This is true regardless of the size of a kite. A kite doesn’t have any right angles inside but the two lateral interior angles are equal.