١٨- قاعدة شَرَائِفُ

If: 

• Word is on the scale of مفاعل
• Harf illah occurs after the alif
• Harf illah is not a root letter

Then

• Change the harf illah to a hamza

Example:

Note:

The changing of a root letter which is harf illah to a hamza is rare

Example: