Descriptive grammars are our main vehicle for documenting and analysing the linguistic structure of the world's 6,000 languages. They bring together, in one place, a coherent treatment of how the whole language works, and therefore form the primary source of information on a given language, consulted by a wide range of users: areal specialists, typologists, theoreticians of any part of language (syntax, morphology, phonology, historical linguistics etc.), and members of the speech communities concerned. The writing of a descriptive grammar is a major intellectual challenge, that calls on...