rhombus, a four-sided, or quadrilateral, geometric figure in which all four sides are of the same length and each of the two pairs of opposite sides are parallel to each other. The word rhombus comes from the Greek rhombos, meaning “a spinning top” or “a piece of wood whirled on a string.” Rhombuses can be seen in everyday life, in applications ranging from traffic signboards to jewelry to interior and exterior design.

　　All four sides of the rhombus are equal in length.Opposite sides of a rhombus are parallel to each other.The two opposite pairs of angles within the rhombus are equal to each other. If one angle is 60°, the opposite angle must also be 60°.Any two adjacent angles (angles next to each other) within the rhombus add up to 180°. For example, if one angle is 55°, the angle next to it will be 125°.A rhombus is also called a diamond. If all four interior angles are 90°, the rhombus becomes a square.The sum of all interior angles of a rhombus is always 360°.If two diagonal lines are drawn across each pair of opposite corners, they will be perpendicular to and bisect (divide into equal halves) each other at an angle of 90°. These diagonal lines will also bisect the angles they pass through. Perimeter and area of a rhombus The perimeter, or distance around the edges, of a rhombus is calculated by multiplying the length of one side of the rhombus by 4.perimeter of a rhombus = 4 × side lengthIf a rhombus has a side length of 4 units, its perimeter will be 16 units:4 × side length = 4 × 4 = 16

　　The area of a rhombus can be calculated using either of two methods. In the first method, the area is calculated by multiplying the side of the rhombus by its altitude (distance between two opposite sides):method 1: area of a rhombus = altitude × side lengthA rhombus with a side length of 5 units and an altitude of 6 units will have an area of 30 square units.method 1: area = 5 × 6 = 30 square unitsThis method can be used when both the side length and the altitude are known.

　　In the second method, instead of the side length, the lengths of the two diagonals (lines joining the pairs of opposite corners) of the rhombus are used. The area is calculated by multiplying the lengths of the two diagonals and dividing by two:method 2: area of a rhombus = length of diagonal 1 × length of diagonal 2/ 2A rhombus with diagonals of length 7 units and 8 units will thus have an area of:method 2: area = 7 × 8/2 = 28 square units

　　Rhombuses in daily life What is a rhombic lattice?A rhombic lattice is a lattice (an interlaced pattern) that has a rhombus as its fundamental design element. Rhombic lattices help portray both two-dimensional and three-dimensional designs. Rhombic lattices are often used in wallpaper, floor and wall tiling, carpeting, and clothing designs. The classic argyle pattern usually seen on socks and sweaters features diamond shapes.

　　Flat gardening and masonry trowels often take the shape of a rhombus. The pointed end makes it easy to dig into the earth or the thick mortar. The broad middle section of the trowel is then used to lift dirt or to lay mortar between bricks or masonry stones.

　　Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now In several countries, including the United States, many traffic departments use diamond-shaped yellow warning signs to indicate potentially dangerous road conditions ahead, such as slippery surfaces, merging lanes, or sharp curves. Other common uses of the rhombus include jewelry designs, as for earrings, pendants, and rings, as well as equilateral kites. A baseball field, or “diamond,” is also a rhombus.

　　Some modern buildings, such as the Crain Communications Building in Chicago, prominently incorporate this geometric figure in their structure. The logo of the Japanese automaker Mitsubishi features three red rhombuses sharing a common vertex.