Nunation

Nunation (Arabic: تَنوِين, tanwīn), in some Semitic languages such as Literary Arabic, is the addition of one of three vowel diacritics (ḥarakāt) to a noun or adjective.

This is used to indicate the word ends in an alveolar nasal without the addition of the letter nūn. The noun phrase is fully declinable and syntactically unmarked for definiteness, identifiable in speech.