Unfortunately, there are even more exceptions to the “every letter has two forms” rule. There are three letters in Persian that have four forms. The choice of which one to use depends not only on whether it is the last letter of the word or not, but also on whether it is attached to its previous letter or not. The following table and the examples will make things more clear.
Free beginning joined end
Joined beginning free end
Free beginning free end
Joined beginning joined end
For all the letters we had seen so far, being joined to the previous letter or not didn’t make a difference. As you see, for these four new letters, it does. Here are some examples:
The letter “ع” is simply a glottal stop.
When coming in the beginning of a word, it has no difference with the case in which the word starts with the letter “ا”. Whether to begin the word with “ا” or with the letter “ع” cannot be predicted by the pronunciation and has to be memorized for each word separately. However, few words begin with “ع” in Persian, almost all of them being Arabic loan words.