jinni, feminine jinniyah, plural jinn, in Arabic and Islamic folklore, spirit or demon endowed with supernatural power. In ancient belief the jinn were associated with the destructive forces of nature. In Islamic tradition they were corporeal spirits similar to men in appearance but having certain supernatural powers, especially those of changing in size and shape. Capable of both good and evil, the jinn were popular in literatures of the Middle East, notably in the stories of the Thousand and One Nights. The term genie is the English form and is sometimes confused with the Roman genius.