"Functional" signifies the proposition that language evolved under pressure of the functions that the language system must serve. Functions are taken to have left their mark on the structure and organisation of language at all levels, which is achieved via metafunctions. "Metafunction" is uniquely defined in SFL as the "organisation of the functional framework around systems", i.e., choices. This is a significant difference from other "functional" approaches, such as Dik's functional grammar (FG, or as now often termed, functional discourse grammar) and lexical functional grammar. To avoid confusion, the full designation—systemic functional linguistics—is typically used, rather than "functional grammar" or "functional linguistics".