What The project is about grammar. Grammar is not something that was invented by evil teachers, but a phenomenon that depends on the people who use it. It is at the same time a social phenomenon (getting your grammar wrong may be socially stigmatizing) and a neurocognitive phenomenon (grammar may be lost or impaired due to brain damage). The project presents a novel, unified theory of what grammar is, how it develops, and what its neurocognitive basis is. The central idea in this theory is that the contrast between grammar and the lexicon serves the function of prioritizing the parts of complex linguistic messages, saving time and processing resources for the language users. Why Grammar is one of relatively few features that distinguish human beings from our closest relatives, and it plays a central role in the evolutionary success of the human species. Understanding its nature is therefore a crucial task both for the language sciences in particular and for the humanities in general. The project aims at giving the first unified account of grammar which simultaneously captures its unique features (emphasized by Chomskyan linguistics) and its integration in a wider communicative and neurocognitive context (emphasized by functional-cognitive linguistics). How Work on the monograph will be conducted by grant-holder Kasper Boye in collaboration with Professor Peter Harder. The work will be of two kinds. Firstly, we will thoroughly revise our 2012 theory of grammatizalization, which forms the basis of the present project, in light of new empircal evidence. Secondly, we will extend the 2012 theory to cover also, for instance, the phylogenesis of grammar (i.e. the emergence of grammar in the human species) and the loss of grammar as a result of brain damage. Our work will consist both in hypothesis formation and in a theoretical synthesis of results obtained in empirical studies over the past 5 years.