noun: (linguistics) One of fourteen Arabic letters that do not affect the pronunciation of the "L" of a preceding definite article (ال- (al--)). The "L" in the Arabic definite article is pronounced "L" when followed by a moon letter: e.g., القُرْآن (al-qurʾān). The fourteen moon letters are: ء (ʾ), ب (b), ج (j), ح (ḥ), خ (ḵ), ع (ʿ), غ (ḡ), ف (f), ق (q), ك (k), م (m), ه (h), و (w), ي (y)