A Fairy is a type of mythological being or legendary creature, a form of spirit, often described as metaphysical, supernatural or preternatural. The word fairy derives from the term fae of medieval Western European Last French folklore and romance, one famous example being Morgan le Fay was therefore everything that appertains to the "fae", and so the land of "fae", all the "fae". Finally the word replaced its original and one could speak of "a faery or fairy", though the word fey is still used as an adjective. 'Fae' is the plural, 'Faery' is the singular.
