Both الْيَتِيمَ and الْمِسْكِينِ have a pronounced article lām: yāʾ and mīm are moon letters.
Each word also contains madd yāʾ, governed by a separate trigger. At a pause on al-yatīm the final mīm becomes sākin; at a pause on al-miskīn the final nūn does. Both thereby create madd ʿāriḍ before the final consonant. Do not confuse lām classification with vowel length.
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Al-yatīm and al-miskīn: clear article lām
Al-Māʿūn and Al-Humazah: Applied Assimilation, Concealment, Madd and Hāʾ Rules
Both الْيَتِيمَ and الْمِسْكِينِ have a pronounced article lām: yāʾ and mīm are moon letters.
Each word also contains madd yāʾ, governed by a separate trigger. At a pause on al-yatīm the final mīm becomes sākin; at a pause on al-miskīn the final nūn does. Both thereby create madd ʿāriḍ before the final consonant. Do not confuse lām classification with vowel length.