What does orthorhombic mean?
Orthorhombic is an adjective used chiefly in crystallography and materials science to describe a structure whose three crystallographic axes meet at right angles but have different lengths. This distinguishes an orthorhombic crystal from a cubic one, whose three axes are equal, and from other crystal systems with different symmetry relationships. The word commonly appears in expressions such as “orthorhombic crystal system,” “orthorhombic structure,” and “orthorhombic lattice.” In everyday geometry, it can refer more generally to forms with unequal perpendicular dimensions, although this broader use is less precise than the crystallographic sense. The term derives from Greek roots associated with straightness or correctness and a rhombus, reflecting the underlying geometric geometry of the forms it describes.
adjectiveRelating to a crystal system or solid in which the three crystallographic axes are at right angles to one another but have different lengths. The term is also used more generally for forms characterized by this arrangement.
- Having three crystallographic axes that are mutually perpendicular and of unequal length, especially in the orthorhombic crystal system.
"The mineral has an orthorhombic crystal structure, with three unequal axes meeting at right angles."
"The compound crystallizes in an orthorhombic lattice."
"Researchers used X-ray diffraction to determine the material's orthorhombic symmetry."
Orthorhombic crystals look boxy at first glance, but their three axes are not equal: the structure is rectangular rather than cubic.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does orthorhombic come from?
The word combines the Greek-derived element ortho-, associated with straight, correct, or right-angled, with rhombic, which comes from Greek rhombos, a diamond-shaped figure. In modern crystallography, the compound developed to name a crystal system characterized by three mutually perpendicular axes of unequal length. Its components also connect it with words such as orthography, orthodontics, rhombus, and rhomboid.
Related word forms
How orthorhombic is actually used
The term is primarily technical, especially in crystallography, mineralogy, chemistry, and materials science. It is occasionally used more broadly for geometric forms with three unequal perpendicular axes, but that usage is less standardized.
Easily confused with orthorhombic
A cubic structure has three equal axes that meet at right angles, whereas an orthorhombic structure has three unequal perpendicular axes.
In crystallography, rhombic refers to the rhombohedral system, whereas orthorhombic specifically describes a system with three unequal perpendicular axes.