One of the many mysteries of Persian dialectology is that, apart from the numerous Arabic and other foreign loanwords in Persian, many Persian words in Persian vocabulary are non-Persian. Comparative grammarians say that the Persian word for king, šāh, is not proper Persian, since the form expected in proper Persian is *šāš. The word for "city", šahr, which in early periods meant "kingdom", should have been *šas in Persian. sang "stone" is most likely *hang instead of big *buhurg, buzurg, and instead of asp 'horse' *as and instead of asmān, sky, *āhmān and even instead of Fārsī Persian, *Pāhlī. All these words and many others that convey the most conventional meanings, contradict one or another rule about what the phonology of the Persian language considers correct, but agree with what is known or can be inferred about the phonology of Median. Accordingly they are declared Median. And they are declared to belong to another non-Persian language, for example Avestan, which considers these words as Median in relation to their ancient Iranian predecessors, because the ancestors of some of them are apparently non-Persian. Already in Old Persian, at some time, about 520 BC, when the Iranians, some time before they had taken over a vast empire from the Medes, were probably influenced by the administrative and generally cultural vocabulary of the Medes.