function shift

function change

noun

grammar a change in the syntactic function of a word, as when the noun mushroom is used as an intransitive verb
linguistics sound change involving a realignment of the phonemic system of a language

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012