 Like its close relatives, the Pahlavi scripts, written Sogdian contains many logograms or ideograms, which were Aramaic words written to represent native spoken ones.The Sogdian script is the direct ancestor of the Old Uyghur alphabet, itself the forerunner of the Traditional Mongolian alphabet.As in other writing systems descended from the Proto-Sinaitic script, there are no special signs for vowels.