Classical Armenian (Grabar), which remained the standard until the 18th century, was quite homogenous across the different regions that works in it were written; it may have been a cross-regional standard. The Middle Armenian variety used in the court of Cilician Armenia (1080-1375) provides a window into the development of Western Armenian, which came to be based on what became the dialect of Istanbul, while the standard for Eastern Armenian was based on the dialect around Mount Ararat and Yerevan. Although the Armenian language is often divided into "east" and "west", the two standards are actually relatively close to each other in light of wealth of the diversity present among regional non-standard Armenian dialects. The different dialects have experienced different degrees of language contact effects, often with Turkic and Caucasian languages; for some, the result has been significant phonological and syntactic changes. Fortson notes that the modern standard as well has now attained a subordinate clausal structure that greatly resembles a Turkic language.