What does rhombus mean?
A rhombus is a geometric quadrilateral with four sides of equal length and opposite sides parallel. It belongs to the family of parallelograms, but unlike a general parallelogram, all four of its sides match; a square is therefore the familiar special case with four right angles, while a slanted rhombus has acute and obtuse angles. In everyday design, a rhombus may be called a diamond, especially when it resembles the shape of a playing card or gemstone. The word is useful in geometry because it identifies this equilateral parallelogram precisely, and in art, tiling, and architecture because rhombic forms create repeated directional patterns. Rhombuses occur naturally in many visual systems, from diamond-shaped floor tiles and heraldic devices to molecular diagrams. When speaking informally, people sometimes use rhombus for any diamond-like quadrilateral, but a mathematical rhombus has the stricter requirement that all four sides be equal. Its familiar first-syllable stress and ancient Greek ancestry also make it one of the more distinctive names in everyday mathematical vocabulary.
nounA parallelogram with four sides of equal length. Every square is a rhombus, but a rhombus need not have right angles.
- A parallelogram whose four sides are all of equal length.
"She drew a rhombus in the centre of the geometric pattern."
"The diagonals of a rhombus intersect at right angles."
"A wall of bright rhombuses gave the room a lively, geometric appearance."
Both plural forms are standard; rhombuses is especially common in general English, while rhombi is frequent in technical and mathematical contexts.
"The designer tiled the wall with bright rhombuses."
Every square is a rhombus—but not every rhombus is a square.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does rhombus come from?
The English noun comes through Latin rhombus, a geometric term for a lozenge or rhombic form. Latin borrowed Greek rhombos, originally associated with a spinning or whirling object and linked to the Greek verb rhembein, “to whirl.” Later English developed related forms such as rhombic and rhomboid, while rhombencephalon reflects the same Greek root in the anatomical term for the hindbrain.
Related word forms
How rhombus is actually used
The word is primarily used in geometry, design, and descriptions of shapes. In informal visual descriptions, “diamond” may be used instead, but rhombus is the more precise geometric term.
Easily confused with rhombus
A rhomboid is a parallelogram with two pairs of equal parallel sides; in a rhombus, all four sides are equal.