In crystallography, the **orthorhombic crystal system** is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base (*a* by *b*) and height (*c*), such that *a*, *b*, and *c* are distinct. All three bases intersect at 90° angles, so the three lattice vectors remain mutually orthogonal.

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## Two-dimensional

There are two orthorhombic Bravais lattices in two dimensions: Primitive rectangular and centered rectangular. The primitive rectangular lattice can also be described by a centered rhombic unit cell, while the centered rectangular lattice can also be described by a primitive rhombic unit cell.

## Three-dimensional

There are four orthorhombic Bravais lattices: primitive orthorhombic, base-centered orthorhombic, body-centered orthorhombic, and face-centered orthorhombic.

In the orthorhombic system there is a second choice of crystal axes that results in a unit cell with the shape of a right rhombic prism, although this axis setting is very rarely used; this is because the rectangular two-dimensional base layers can also be described with rhombic axes. In this axis setting, the primitive and base-centered lattices interchange in centering type, while the same thing happens with the body-centered and face-centered lattices.

## Crystal classes

The *orthorhombic crystal system* class names, examples, Schönflies notation, Hermann-Mauguin notation, point groups, International Tables for Crystallography space group number, orbifold notation, type, and space groups are listed in the table below.