Second...

Second, if it is after two letters, the first yā' is erased and the second is changed into a wāw and the letter before it is given a fathah , for example: نَبيّ becomes نَبَوِيّ. Third, if it is after three or more letters the word remains the same, for example: کرسي becomes کرسيٌ. If the noun is in the form فعیلة and one wants to make it into a possessive noun the yā' is erased and the letter before it is given a fathah , for example: مدینة becomes مَدَنيّ.

The exception to this rule is if the second root letter is weak or doubled, in this case the yā' is not erased, for example: طَوِیلة becomes طَویليّ. If the noun is a trilateral noun whose third letter is erased and two letters remain and one wants to make it into a possessive noun the erased letter returns in the possessive form, for example: أب becomes أبَويّ.

If a feminine tā' replaces the erased letter, it will be erased and the original letter will be brought back, for example: سنة becomes سنويّ. Previous…