What are the 4 rules of Tajweed?

Tajweed Rules for Noon Saakin and Tanween

To accurately articulate Noon Saakin and Tanween when they appear with other letters, Tajweed prescribes four main rules: Izhar, Idgham, Iqlab, and Ikhfaa. The rule of Izhar clearly pronounces Noon Saakin or Tanween when followed by specific throat letters. Meanwhile, Idgham involves the merging of Noon Saakin or Tanween with particular letters, which can occur either with or without a nasal sound (ghunna).