This article needs attention from an expert in linguistics.(January 2010)
This is used to indicate the word ends in an alveolar nasal without the addition of the letter n?n. The noun phrase is fully declinable and syntactically unmarked for definiteness, identifiable in speech.
When writing Literary Arabic in full diacritics, there are three nunation diacritics, which indicate the suffixes -un (IPA: /-un/) (nominative case), -in /-in/ (genitive), and -an /an/ (accusative). The orthographical rules for nunation with the fat?ah sign is by an additional ? alif (, diacritic above alif; or , diacritic before alif), above (t marbah ) or above (hamzah ?).
In spoken Arabic, nunation only exists in words and phrases borrowed from the literary language, especially those that are declined in the accusative (that is, with -an).
Since Arabic has no indefinite article, nouns that are nunated are indefinite, and so the absence of the definite article 'al triggers nunation in all nouns and substantives except diptotes (that is, derivations with only two cases in the indefinite state, -u in the nominative and -a in the accusative and genitive). A given name, if it is not a diptote, is also nunated when declined, as in ? ? ? (ashhadu anna Mu?ammadan ras?lu l-l?h(i) /?a?.ha.du ?an.na mu.?am.ma.dan ra.su:.lul.la:(.hi)/ "I bear witness that Muhammad is the messenger of Allah."), in which the word ? Mu?ammad, a given name derived from the passive participle of ? ("to praise"), is nunated to ? Mu?ammadan to signal that it is in the accusative case, as it is the grammatical subject of a sentence introduced by ? ("that").