The operation in آمَنَ، أُومِنَ، إِيمَانًا has a precisely defined cause: two hamzahs in one word, with the second quiescent.
It does not follow that any pair of written hamzahs may simply be dropped. Different vowel settings can invoke different rules.
Nor are substitution and deletion identical. In آمَنَ, the second hamzah is replaced by a corresponding long-vowel element; the analysis is not merely “remove a letter without replacement.”
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Scope of the Two-Hamzah Rule
Rules of Hamzated Forms: Lightening, Substitution, Elision and Short Paradigms
The operation in آمَنَ، أُومِنَ، إِيمَانًا has a precisely defined cause: two hamzahs in one word, with the second quiescent.
It does not follow that any pair of written hamzahs may simply be dropped. Different vowel settings can invoke different rules.
Nor are substitution and deletion identical. In آمَنَ, the second hamzah is replaced by a corresponding long-vowel element; the analysis is not merely “remove a letter without replacement.”