1. Idhaar - if you see a noon saakinah or tanween, and after it one of these letters: hamzah, ha, 'ain, Ha, ghain or kha, then read the noon sound clearly.
2.Idghaam with Ghunnah - this is when the noon saakinah or tanween partially merges into the next letter, with the two letters being pronounced as one. The letters of Idghaam with Ghunnah are: meem, noon, wow and ya.
2.Idghaam without Ghunnah - this is when the noon saakinah or tanween fully merges into the next letter, either ra or laam. The noon is not pronounced at all.