الْتِقاءُ السَّاكِنَيْنِ

“The meeting of two unvowelled letters”: This occurs when two consecutive letters in a word or between two words both have a سُكُونٌ (a diacritical mark indicating no vowel). Arabic phonology generally avoids this sequence, often resolving it by omitting the first unvowelled letter (especially if it’s a long vowel) or by assigning a temporary (helping) vowel to the first of the two letters.