Tanwīn is an extra final /n/ sound represented by double vowel marks rather than a separate written nūn, as in «زَيْدٌ».
زَيْدٌ، زَيْدًا، زَيْدٍ — ordinary case endings with tanwīn.
عُمَرُ، عُمَرَ، عُمَرَ — no ordinary tanwīn.
Caution: The absence of tanwīn alone does not prove that a noun is a diptote: nouns with «ال» and nouns in iḍāfa also commonly lack tanwīn.
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Noun Case Classes: Type 3 — Diptote (Ghayr Munṣarif)
Tanwīn is an extra final /n/ sound represented by double vowel marks rather than a separate written nūn, as in «زَيْدٌ».
زَيْدٌ، زَيْدًا، زَيْدٍ — ordinary case endings with tanwīn.
عُمَرُ، عُمَرَ، عُمَرَ — no ordinary tanwīn.
Caution: The absence of tanwīn alone does not prove that a noun is a diptote: nouns with «ال» and nouns in iḍāfa also commonly lack tanwīn.