As part of the phonetic development of Adûnaic, over-long vowels were sometimes produced in Primitive Adûnaic by the contact of identical vowels “where one of the merged vowels was already long” (SD/423). Such vowels also appeared as variant forms of biconsonantal roots (SD/423). In Lowdham’s Report, Tolkien used the macron (ā) for long vowels and the circumflex (â) for over-long vowels, though he was not entirely consistent in his notation.

Tolkien said these vowels were recognized “in the older language” but did not specify how they applied to speech by the time of Classical Adûnaic. It seems likely that over-long vowels would have been reduced to ordinary long vowels by the time of Classical Adûnaic. In his later writings, Tolkien used the circumflex for ordinary long vowels in Adûnaic, as he did for all of his non-Elvish languages.

The discussions uses the macron for ordinary long vowels in Primitive Adûnaic and the circumflex for ordinary long vowels in Classical Adûnaic. The primitive over-long vowels are frequently omitted, since these would eventually reduce back to ordinary long vowels.