Proto-Semitic had a simple vowel system, with three qualities *a, *i, *u, and phonemic vowel length, conventionally indicated by a macron: *ā, *ī, *ū. This system is preserved in Akkadian, Ugaritic and Classical Arabic.
The reconstruction of Proto-Semitic was originally based primarily on Arabic, whose phonology and morphology (particularly in Classical Arabic) is extremely conservative, and which preserves …

The phonologies of the attested Semitic languages are presented here from a comparative point of view. See Proto-Semitic language#Phonology for details on the phonological reconstruction of Proto-Semitic used in this article. The reconstruction of Proto-Semitic (PS) was originally based primarily on Arabic, whose phonology and morphology (particularly in Classical Arabic) is very conservative, and which preserves as contrastive 28 out of the evident 29 consonantal phoneme…