Rz

Rz is a two-letter symbol that appears in different fields with different meanings. In mathematics, physics, and computer graphics, Rz denotes a rotation about the z-axis. The standard rotation matrix for a rotation by angle θ around the z-axis is Rz(θ) = [[cosθ, -sinθ, 0], [sinθ, cosθ, 0], [0, 0, 1]]. This transformation preserves the z-coordinate while rotating the x–y plane. A positive angle corresponds to a counterclockwise rotation when looking from the positive z direction, following the right-hand rule. Rz is often used alongside similar rotations about the x- and y-axes to describe general 3D orientation changes.

In computing, rz is a command from the lrzsz suite used to receive files via the ZMODEM protocol in terminal sessions. It is typically paired with the sz command, which is used to send files. These tools are common in Unix-like environments for interprocess file transfer over serial connections or terminal emulators.

In linguistics, "rz" is a digraph found in several Slavic languages, most notably Polish, where the sequence commonly represents a single phoneme, typically the voiced retroflex fricative /ʐ/. The digraph is treated as a unit in spelling and pronunciation, though phonetic realization can vary by language and dialect.

Rz can also function as an acronym or code in various specialized contexts, so its meaning is highly dependent on the domain. The term is not tied to a single universal definition.