quality:corruption, structural:summarization, structural:expansion, linguistic:translation
Consonantal root structures

A widely attested feature in AA languages is a consonantal structure into which various vocalic "templates" are placed. This structure is particularly visible in the verbs, and is particularly noticeable in Semitic. Besides for Semitic, vocalic templates are well attested for Cushitic and Berber, where, along with Chadic, it is less productive; it is absent in Omotic. For Egyptian, evidence for the root-and-template structure exists from Coptic. In Semitic, Egyptian, Berber, verbs have no inherent vowels at all; the vowels found in a given stem are dependent on the vocalic template. In Chadic, verb stems can include an inherent vowel as well.

Most Semitic verbs are triliteral (have three consonants), whereas most Chadic, Omotic, and Cushitic verbs are biliteral (having two consonants). The degree to which the Proto-AA verbal root was triliteral is debated. It may have originally been mostly biconsonantal, to which various affixes (such as verbal extensions) were then added and lexicalized. Although any root could theoretically be used to create a noun or a verb, there is evidence for the existence of distinct noun and verb roots, which behave in different ways.

As part of these templates, the alternation (apophony) between high vowels (e.g. i, u) and a low vowel (a) in verbal forms is usually described as one of the main characteristics of AA languages: this change codes a variety of different functions. It is unclear whether this system is a common AA trait; the Chadic examples, for instance, show signs of originally deriving from affixes, which could explain the origins of the alterations in other languages as well.