Zeta is the sixth letter of the Greek alphabet, represented by the symbol Ζ in uppercase and ζ in lowercase. In the Greek numeral system, it has a value of 7. Zeta is often used in mathematics and science to denote various concepts, such as the Riemann zeta function, which is important in number theory. In addition to its mathematical significance, Zeta is also used in various fields, including engineering and physics. For example, in fluid dynamics, Zeta can refer to a damping ratio in control systems. The letter is also commonly found in names of organizations and products, such as Zeta Tau Alpha, a sorority.