جَاءَ أَحْمَدُ. — Aḥmad came.
جَاءَ: past verb, built on fatḥa.
أَحْمَدُ: subject, nominative with ḍamma.
Because Aḥmad is diptote, it bears one ḍamma, not nominative tanwīn.
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Aḥmad in the Nominative
Diptote Causes — Verb Patterns and Their Conditions
جَاءَ أَحْمَدُ. — Aḥmad came.
جَاءَ: past verb, built on fatḥa.
أَحْمَدُ: subject, nominative with ḍamma.
Because Aḥmad is diptote, it bears one ḍamma, not nominative tanwīn.