The source contrasts heavy emphatic nūn (doubled nūn) with light emphatic nūn (sukūn-bearing nūn). Both strengthen the assertion but take different endings:
لَيَدْعُوَنَّ — he will certainly call (heavy).
لَيَدْعُوَنْ — he will certainly call (light).
لَيَدْعُوَانِّ — emphatic dual masculine third person.
Person/number endings interact with the weak-final stem; one cannot simply append the same characters to every imperfect. The source marks some light-nūn cells with dashes rather than supplying active forms.
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Heavy and Light Emphatic Nūn
Defective Wāw Verb: Full Paradigm of دَعَا يَدْعُو with Morphological Explanations
The source contrasts heavy emphatic nūn (doubled nūn) with light emphatic nūn (sukūn-bearing nūn). Both strengthen the assertion but take different endings:
لَيَدْعُوَنَّ — he will certainly call (heavy).
لَيَدْعُوَنْ — he will certainly call (light).
لَيَدْعُوَانِّ — emphatic dual masculine third person.
Person/number endings interact with the weak-final stem; one cannot simply append the same characters to every imperfect. The source marks some light-nūn cells with dashes rather than supplying active forms.