[Gr. ζῆτα, the letter Ζ, ζ: see Z.] Name of the sixth letter of the Greek alphabet, used attrib. in zeta-function Math., one of a set of functions (denoted by a capital Ζ prefixed to the variable) connected with elliptic integrals. Hence Zetacism [cf. ETACISM, LAMBDACISM, RHOTACISM], frequent or faulty use of the letter ζ; Zetaic a. Math., applied by Sylvester to operations (denoted by the letter ζ prefixed to an expression) in which subscript indices are treated like ordinary indices of powers, and to expressions or functions so obtained.
1840. Sylvester, Coll. Math. Papers (1904), I. 47. I use the Greek letter ζ to denote that the product of factors to which it is prefixed is to be effected after a certain symbolical manner. This I shall distinguish as the zeta-ic product. Ibid. Rule for zeta-ic multiplication. Note. An analogous interpretation may be extended to any zeta-ic function whatever.
1889. I. Taylor, Aryans, v. § 1. 260. The tendency to Zetacism among the Ionians may be due to an admixture with the pre-Aryan population.
