Fifty in English is spelled "fifty." The pronunciation of "fifty" is [ˈfɪfti] in British English and [ˈfɪfti] in American English. It refers to the number fifty, fifty items, or something numbered fifty. As an adjective, it describes something related to fifty or fifty items. The plural form is "fifties." Common phrases include "fifty pence" (fifty British pence), "fifty-fifty" (which means equal division), and "on a fifty-fifty basis" (meaning on an equal basis).
The term "fiftieth" in English is pronounced [ˈfɪftiɪθ]. It refers to the fiftieth in a series or the fiftieth anniversary of an event. For example: "The foundations grew quickly during the nineteen forties and fifties." This sentence describes the growth occurring in the 1940s and 1950s. Phrases such as "one fiftieth" (one part in fifty) and "Fiftieth Anniversary National Committee" are also used. "The fiftieth day" would refer to the fifty-first day counting from a specific starting point.
