ad-Din

Ad-Din (Arabic: الْدِّين‎ ad-dīn  "(of) the Religion/ Faith/ Creed"), a suffix component of some Arabic names, meaning "the religion/faith/creed", e.g. Saif al-Din (Arabic: سيف الدّين‎, romanized: Sayf al-Dīn, lit. 'Sword of the Faith').

The Arabic spelling in its standard transliteration is ad-Din, due to the phonological rules involving "sun letter" (حرف الشّمسيّة hurfu ’sh-Shamsiyyah), the Arabic letter د (dāl) is assimilated letter of the ِArabic definite article ال (al). The first noun of the compound must have the ending -u which according to the assimilation rules in Arabic - names in general is in the nominative case, assimilates the following a-, thus manifesting into ud-Din in Classical and Modern Standard Arabic.

However, all the modern Arabic vernaculars lack the noun endings, thus the vowel of the definite article in them is pronounced in full as either a or e (the latter mostly in Maghreb and Egypt). At the same time the Arabic short vowel u is rendered as short o in Persian, thus od-din.

So in practice romanizations of Arabic names containing this element may vary greatly, including:

• al-Din, ad-Din, -addin, -adin
• el-Din, -eldin, -eddin
• ud-Din, -uddin (particularly in English-speaking South and East Asia), -uddeen (particularly in English-speaking South and East Asia)
• -eddine (particularly in French-speaking areas)
• -ettin (particularly in Turkish names)
• -od-din (particularly in Persian names)

Examples of names including this element are: