Functional shift

In linguistics, functional shift occurs when an existing word takes on a new syntactic function. For example, the word like, formerly only used as a preposition in comparisons (as in "eats like a pig"), is now also used in the same way as the subordinating conjunction as in many dialects of English (as in "sounds like he means it"). The boundary between functional shift and conversion (the derivation of a new word from an existing word of identical form) is not well-defined.