Dictionary Definition
rhombus n : a parallelogram with four equal
sides; an obliqueangled equilateral parallelogram [syn: rhomb] [also: rhombi (pl)]
User Contributed Dictionary
English
Etymology
First coined 1567, from rhombus < ῥόμβος < ῥέμβομαιNoun
 A parallelogram having all sides of equal length.
Translations
A parallelogram having all sides of equal length
Latin
Etymology
From ῥόμβος < ῥέμβομαιNoun
rhombusExtensive Definition
In geometry, a rhombus (from
Ancient
Greek ῥόμβος  rrhombos, “rhombus, spinning top”), (plural
rhombi or rhombuses) or rhomb (plural rhombs) is an equilateral
quadrilateral. In
other words, it is a foursided polygon in which every side has the
same length.
The rhombus is often casually called a diamond,
after the diamonds
suit in playing cards, or a lozenge, because those shapes
are rhombi (though not all rhombi are actually diamonds or
lozenges).
Supersets
In any rhombus, opposite sides are parallel. Thus, the rhombus is a special case of the parallelogram. One analogy holds that the rhombus is to the parallelogram as the square is to the rectangle. In its turn, the square is a special case of the rhombus, being most readily defined as a rhombus with one right angle.A rhombus is also a special case of a kite (a
quadrilateral with two distinct pairs of adjacent sides of equal
lengths). The opposite sides of a kite are not parallel unless the
kite is also a rhombus.
Area=() /2
Because the rhombus is a parallelogram, the area
also equals the length of a side (B) multiplied by the
perpendicular distance between two opposite sides(H)
Area=B \times H
The area also equals the square of the side
multiplied by the sine of any of the interior angles:
Area=
where a is the length of the side and \theta is
the angle between two sides.
A proof that the diagonals are perpendicular
One of the five 2D lattice types is the rhombic lattice, also called centered rectangular lattice.If A, B, C and D were the vertices
of the rhombus, named in agreement with the figure (higher on this
page). Using \overrightarrow to represent the vector
from A to B, one notices that \overrightarrow = \overrightarrow +
\overrightarrow \overrightarrow = \overrightarrow+ \overrightarrow=
\overrightarrow \overrightarrow. The last equality comes from the
parallelism of CD and AB. Taking the inner
product, =

 =  + 
 = 0
Tilings
Origin
The word rhombus is from the Greek word for something that spins. Euclid used ρόμβος (rhombos), from the verb ρέμβω (rhembo), meaning "to turn round and round". Archimedes used the term "solid rhombus" for two right circular cones sharing a common base.References
External links
 Parallelogram and Rhombus  Animated course (Construction, Circumference, Area)
 Rhombus definition. Math Open Reference With interactive applet.
 Rhombus area. Math Open Reference Shows three different ways to compute the area of a rhombus, with interactive applet.
rhombus in Arabic: دالتون(رياضيات)
rhombus in Asturian: Rombu
rhombus in Azerbaijani: Romb
rhombus in Bosnian: Romb
rhombus in Bulgarian: Ромб
rhombus in Catalan: Rombe
rhombus in Czech: Kosočtverec
rhombus in Danish: Rombe
rhombus in German: Raute
rhombus in Estonian: Romb
rhombus in Modern Greek (1453): Ρόμβος
rhombus in Spanish: Rombo
rhombus in Esperanto: Rombo
rhombus in French: Losange
rhombus in Galician: Rombo
rhombus in Korean: 마름모
rhombus in Croatian: Romb
rhombus in Italian: Rombo (geometria)
rhombus in Hebrew: מעוין
rhombus in Georgian: რომბი
rhombus in Haitian: Lozanj
rhombus in Latvian: Rombs
rhombus in Lithuanian: Rombas
rhombus in Limburgan: Roet
rhombus in Hungarian: Rombusz
rhombus in Mongolian: Ромб
rhombus in Dutch: Ruit (meetkunde)
rhombus in Japanese: 菱形
rhombus in Norwegian: Rombe
rhombus in Central Khmer: ចតុកោណស្មើ
rhombus in Low German: Ruut
rhombus in Polish: Romb
rhombus in Portuguese: Losango
rhombus in Romanian: Romb
rhombus in Quechua: Puytu
rhombus in Russian: Ромб
rhombus in Sicilian: Rummu
rhombus in Simple English: Rhombus
rhombus in Slovenian: Romb
rhombus in Serbian: Ромб
rhombus in Finnish: Neljäkäs
rhombus in Swedish: Romb
rhombus in Vietnamese: Hình thoi
rhombus in Ukrainian: Ромб
rhombus in Vlaams: Rute
rhombus in Chinese: 菱形