Wiktionary
maddah
n. 1 Arabic diacritic similar in appearance to a tilde. Over an alif ((m ar آ) "alif maddah"), it indicates glottal stop, /ʔ/, followed by a long /aː/. The diacritic is not used separately, only over alif. Alif maddah can appear in the beginning: (l ar آسف tr=ʾāsif) or in the middle of a word: (l ar قرآن tr=qurʾān). 2 In the Qur'an, it indicates an extra long vowel and can appear over any long vowel. 3 In Persian the letter is used only in the beginning of a word with a long /aː/: (l fa آمدن tr=âmadan)