Zeta (UK: , US: ; uppercase Ζ, lowercase ζ; Ancient Greek: ζῆτα, Demotic Greek: ζήτα, classical [d͡zɛ̌ːta] or [zdɛ̌ːta] zē̂ta; Modern Greek: [ˈzita] zíta) is the sixth letter of the Greek alphabet. In...