Are the letters of madd (prolongation) considered letters of illah (weak letters/vowels)? And what are the alif and waw in the words (yakhsha, yadu) called – are they referred to as letters of madd or letters of illah in the state of sukoon (quiescence)? And what do we consider the waw and ya when they are vocalized, as in (qudiya, daawa, yaduwan)? And are the letters of illah considered letters of leen (softness)?

The waw, ya, and alif are absolutely called " حروف علة" (weak letters or letters of 'illa). If they are

sukooned after a vowel that suits them (fatha for alif, damma for waw, and kasra for ya), they are called " حروف لين ومد وعلة" (letters of softness, prolongation, and 'illa). If they are sukooned after a vowel that does not suit them, they are only "لين وعلة" (softness and 'illa). If they are vowelled (تحركت), they are only "حروف علة" (letters of 'illa). They are named as such due to their frequent change and alteration. The letters of prolongation (حروف المد) are so called because the sound extends with them, and the letters of softness (حروف اللين) are so called due to their ease. The waw and alif in "يخشى ويدعو" are letters of 'illa, prolongation, and softness. The ya in "قُضيَ" and the waw in "دعوا ويدعوان" are letters of 'illa and are not letters of softness or prolongation because they are vowelled.