Metafunction
The term metafunction originates in systemic functional linguistics and is considered to be a property of all languages. Systemic functional linguistics is functional and semantic rather than formal and syntactic in its orientation. As a functional linguistic theory, it claims that both the emergence of grammar and the particular forms that grammars take should be explained "in terms of the functions that language evolved to serve". While languages vary in how and what they do, and what humans do with them in the contexts of human cultural practice, all languages are considered to be shaped and organised in relation to three functions, or metafunctions. Michael Halliday, the founder of systemic functional linguistics, calls these three functions the ideational, interpersonal, and textual.