As consonant disappeared (such as [ʔ], [ɣ]) or became vocalic ([w], [j]), once separate vowels could come into contact. In the case where those vowels were the same, they would contract into a single vowel, lengthening in the process (SD/424). This rule seems to have remained functional throughout the development from primitive to Classical Adûnaic. In cases where one of the vowels was already long, this would produce over-long-vowels in older forms of the language (SD/423), though apparently these were reduced to ordinary long vowels by the time of Classical Adûnaic.