Zeta (Ζ, ζ) Definition

Zeta (Ζ, ζ) is the sixth letter of the Greek Alphabet. In the system of of Greek Numerals, it has a value of 7. It was derived from the Phoenician letter zayin. Letters that arose from zeta include the Roman Z and Cryillic 3.
Unlike the other Greek letters, this letter did not take its name from the Phoenician letter from which it was derived; it was given a new name on the pattern of beta, eta and theta. The word zeta is the ancestor of zed, the name of the Latin letter Z in Commonwealth English. Swedish and many Romanic languages (such as Italian and Spanish) do not distinguish between the Greek and Roman forms of the letter. Zeta is used to refer to the Roman letter Z as well as the Greek letter.
Usage in Mathematics & Science
The uppercase zeta is not used, because it is normally identical to Latin Z. The lower case letter can be used to represent:
The Riemann zeta function in mathematics.
The damping ratio of an oscillating system in engineering and physics.
The rotational quantity of angular jerk in physics.
The effective nuclear charge on an electron in quantum chemistry.
The electrokinetic potential in colloidal systems.
The lag angle in helicopter blade dynamics.
Relative vorticity in the atmosphere and ocean.
A number whose discrete values (eigenvalues) are the positive roots of transcendental equations, used in the series solutions for transient one-dimensional conduction equations.
The heat flux across or through a plane (industrial materials technology).
The Weierstrass zeta-function.
In physical chemistry equilibrium computations (using lower case Zeta (ζ)), the extent of reaction.
Greek Alphabet
The letters of the Ancient Greek Alphabet, which are frequently utilized in math and science:
Related Definitions
Sources
“Zeta.” Wikipedia, Wikimedia Foundation, 12 Apr. 2020, en.wikipedia.org/wiki/Zeta.