مد لازم is a term in Arabic phonetics that refers to a prolonged vowel sound that occurs in certain words. It is an essential aspect of Arabic pronunciation, where the length of the vowel can change the meaning of a word. For example, the difference between "كَتَبَ" (kataba) and "كَتَّبَ" (kattaba) illustrates how vowel length can affect interpretation. In Arabic script, مد لازم is represented by specific letters and symbols that indicate the lengthening of the vowel. This concept is crucial for proper recitation of the Quran and is taught in Tajweed, the rules governing the pronunciation of the Quranic text. Understanding مد لازم helps learners improve their Arabic reading and speaking skills.