Monophthongization led to the disappearance of certain diphthongs such as and which were leveled to and , respectively, though Colin hypothesizes that these diphthongs remained in the more mesolectal registers influenced by the Classical language. Alternatively in higher registers, and were only allophones of and respectively, while diphthongs were mostly resistant to monophthongization. However, could turn into or via "imāla". In the presence of velar or pharyngeal contour, was backed into and sometimes even rounded into or , or even . This is evidenced by occasional Romance or even local Arabic transcription of as or .