وَهُمَا يَسْقُطَانِ عِنْدَ الْإِضَافَةِ.
Translation: And both nūns are dropped when the forms enter iḍāfa (the construct phrase).
طَالِبَانِ → طَالِبَا الْعِلْمِ: the dual loses its nūn upon becoming muḍāf.
مُسْلِمُونَ → مُسْلِمُو الْمَدِينَةِ: the sound masculine plural loses its nūn in iḍāfa.
Scope: This dropping applies to the dual and sound masculine plural; not to every noun ending in nūn.
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Noun Case Classes: Type 6 — Sound Masculine Plural and Related Forms
وَهُمَا يَسْقُطَانِ عِنْدَ الْإِضَافَةِ.
Translation: And both nūns are dropped when the forms enter iḍāfa (the construct phrase).
طَالِبَانِ → طَالِبَا الْعِلْمِ: the dual loses its nūn upon becoming muḍāf.
مُسْلِمُونَ → مُسْلِمُو الْمَدِينَةِ: the sound masculine plural loses its nūn in iḍāfa.
Scope: This dropping applies to the dual and sound masculine plural; not to every noun ending in nūn.