▪ I. ‖ zeta1 Antiq.
(ˈziːtə)
[med.L., = diæta (see Z), a. Gr. δῑ́αιτα way of living, dwelling (see diet n.).]
A term of disputed meaning (see quots.).
| 1706 Phillips (ed. Kersey), Zeta,..a Room kept warm like a Stove; a withdrawing-Chamber with Pipes convey'd along in the Walls, to receive from below, either the cool Air, or the heat of warm Water. In our old Records, it is taken for a Dining-Room, Hall, or Parlour. 1849–50 Weale's Dict. Terms, Zeta, presumed to be a room over the porch of a Christian church. 1860 Mayne Expos. Lex., Zeta, Zeteorila [? Zeticula],..the Vaporaria and Conclavia, or vapour-baths and inner closets, in the pavement of which warm or cold water was diffused as required. |
▪ II. ‖ zeta2
(ˈziːtə)
[Gr. ζῆτα, the letter Ζ, ζ: see Z.]
1. 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 Z prefixed to the variable) connected with elliptic integrals.
2. zeta potential Physical Chem., the potential difference that exists across the electrical double layer at the interface of a solid and a liquid.
| 1939 E. A. Hauser Colloidal Phenomena ix. 91 In simple cases, this double layer can be regarded as an electric condenser, the potential of which is generally termed electrokinetic, or ζ (zeta), potential. 1982 Nature 21 Jan. 267/2 They [sc. electrokinetic phenomena] arise whenever there is relative motion between a charged interface and a liquid and are usually interpreted in terms of the zeta potential. |
Hence ˈzetacism (-sɪz(ə)m) [cf. etacism, lambdacism, rhotacism], frequent or faulty use of the letter ζ; zetaic (ziːˈteɪɪk) 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. |