Idgham without ghunnah is a rule in Arabic phonetics, particularly in the context of Tajweed, which governs the pronunciation of certain letters. It occurs when the letter ر (ra) or ل (lam) follows a letter that has a sukun (no vowel sound). In this case, the preceding letter merges into the following letter without any nasal sound, known as ghunnah. This rule is applied to create a smoother transition between sounds, enhancing the flow of recitation. It is important for those studying Quranic recitation to master this rule to ensure proper pronunciation and adherence to the rules of Tajweed.