Izhar means clearness :
Pronounce each letter from the expression point without Ghunnah on the clear letter.
There are six letters when followed by Noon Sakinah or Tanween causes the noon to be said clearly.
These letters are known as the Throat Letters which are: ء هـ ح خ ع غ
If one of the six letters above comes after the noon in one word or comes next to it in the following word, therefore the noon will be said clearly.
-Hamza : كفارٍ أَثيمٍ
-Ha’ : جُرُفٍ هَارٍ
– Ain : سوآءٌ عَليهمْ
– Ghin : وربٌ غَفورٌ
-Haa’ : عليمٌ حَكيمٌ
-Khaa’ : يَوْمَئِذٍ خَاشِعَةٌ