Diyari () or Dieri () is an Australian Aboriginal language spoken by the Diyari people in the far north of South Australia, to the east of Lake Eyre. It was studied by German Lutheran missionaries who translated Christian works into the language in the late 19th and early 20th centuries, so that it developed an extensive written form. Only a few fluent speakers of Diyari remained by the early 21st century, but a dictionary and grammar of the language was produced by linguist Peter K. Austin, and there is a project under way to teach it in schools. Related languages Sign language The Diyari had a highly developed sign language. This was first noticed by Alfred William Howitt in 1891, who first mistook them for defiant or command gestures until he then realised that they formed part of an integral system of hand signs, of which he registered 65. One of their functions was to allow women to communicate during mourning, when a speech taboo prevailed. Dialects Dhirari (extinct late 20th century) was a dialect of Diyari. Austin identified two variants of Dhirari, Southern and Northern, differing only in vocabulary. Pilatapa (extinct by the 1960s) may also have been a dialect; data is poor. Region spoken Diyari was traditionally spoken by the Diyari (or Dieri) people in the far north of South Australia, to the east of Lake Eyre. The mostly dry Cooper Creek and the Birdsville Track run through this very arid region. The whole area was occupied by the Diyari and many place names and mythological sites still exist. Current Dieri speakers live in Marree, Port Augusta, Broken Hill, and Adelaide. Documentation and revival Mission work In 1867 German Lutheran pastors established a Christian mission station and sheep station at Lake Killalpaninna on Cooper Creek, known as Killalpaninna Mission or Bethesda Mission, which was closed by the South Australian government in 1914. The missionaries studied the language and used it, including preaching in Dieri and teaching it in the mission school from 1868. The earliest written records of the language date from 1870, by early missionaries Koch and Homann. Johann Georg Reuther and Carl Strehlow created dictionaries and other teaching aids in Diyari between 1895 and 1906, and translated a large number of Christian works into the language. Reuther translated the New Testament into Diyari, as well as compiling a lengthy manuscript on the language, culture, mythology and