Theta (UK: /ˈθiːtə/, US: /ˈθeɪtə/; uppercase Θ or ϴ, lowercase θ (which resembles digit 0 with horizontal line) or ϑ; Ancient Greek: θῆτα thē̂ta [tʰɛ̂ːta]; Modern: θήτα thī́ta [ˈθita]) is the eighth letter of the Greek alphabet, derived from the Phoenician letter Teth Phoenician teth.svg. In the system of Greek numerals it has the value 9.