What is jimlatul iywaa?

Question
What is jimlatul iywaa? It is in one of the chapters in d book hidayatul muriid. D chapta is 'babu hamzatul mufrad.

Answer
This is referring to the riwaayah of Warsh.  He exchanges the hamzah saakinah into a medd letter when the hamzah comes from the first letter of the root word (fa' al-kalimah) except for when the hamzah saakinah is in a word which is the derivative of , which are words such as: , and

This is specific for the riwaayah of Warsh, and does not have any input in the riwaayah of Hafs. 
If you are studying Warsh or want to know more, you can find more information at the following link:
http://www.abouttajweed.com/warsh/lesson-six.html