(also: shi'a, shi'i, shi'ite) The Shi’at ‘Ali (the party of ‘Ali, for which Shi’ah is an abbreviation and from which the adjective Shi’i comes) believed that the Prophet Muhammad designated his son-in-law ‘Ali and his descendants to be leader (imam) of the ummah after his death. The imam is regarded as an infallible interpreter of the revelation as well as the political leader. The various groups of Shi’i Muslims comprise about 15 percent of Muslims today.