The present article aims at studying the vowels of Persian Language and their phonotactic differences. Many Iranian linguists divide the vowels of Persian into two categories, the long vowels , which have two time-values, and the short ones which have one time-value. The long vowels are twice the short vowels in time of articulation. However, vowel duration is not sensed clearly in written or spoken Farsi. It is just noticed when scanning meter and rhythm of classical poems like that of, say, Hafiz, Sa’di, and Mowlavi. Dividing a line of a poem is done based on the length and duration of the syllables.
The present article investigates the binarity (phonotactically) of the vowel classes in Farsi. We studied the consonantal clusters following the six vowels in different structures. According to the findings of the research, the vowels , and the vowels make two natural classes.