# Z

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff) The letter Z, the twenty-sixth letter of the 26-letter English alphabet, derived from the Phoenician "zayin" symbol. 

In symbols, Z, twenty-sixth letter of the 26th letter English alphabet, is the symbol for []

## Mathematics

In mathematics, "z", lower case, is the symbol for the vertical axis in the Cartesian coordinate system.

## Thermodynamics

In 1875, Rudolf Clausius employed upper “Z” and lower case “z” in his derivation of the forces involved in the work function of a moving body: 

[math]F (xyz) + const[/math]

In words:

“W is the work done whenever a body moves under the influence of a force. The product of the force and distance moved through is the mechanical work which the force performs during the motion.”
— Rudolf Clausius (1875), The Mechanical Theory of Heat (§: Mathematical Introduction)

In 1924, James Partington, was employing the symbol "Z" thusly: “Z is called the thermodynamic potential by analogy with the potential function in dynamics: ϕ1 – ϕ2 = work”, was employed as the symbol for the isothermal-isobaric thermodynamics potential: 

[math]U – TS + pV[/math]

In other words, Z, at one point was a symbol for the Gibbs energy, in modern parlance. 

The letter “Z” is also sometimes employed as the “compressibility factory” of a gas.