Imperial Aramaic

The Ancient Aramaic alphabet is adapted from the Phoenician alphabet and it became distinctive from it by the 8th century BC. It was used to write the Aramaic language. All the letters represent consonants, some of which are matres lectionis, which also indicate long vowels.

The Aramaic alphabet is historically significant, since virtually all modern Middle Eastern writing systems can be traced back to it, as well as numerous non-Chinese writing systems of Central and East Asia. This happens because of the widespread usage of the Aramaic language as both a lingua franca and the official language of the Neo-Assyrian Empire, and its successor, the Achaemenid Empire. Among the scripts in modern use, the Hebrew alphabet bears the closest relation to the Imperial Aramaic script of the 5th century BC, with an identical letter inventory and, for the most part, nearly identical letter shapes.

In relation to this, Peter T. Daniels introduced a term called abjad. What does it mean? Abjadas are writing systems that indicate consonants but do not indicate most vowels (like Aramaic) or indicate them with added diacritical signs. Clearly we're having case of an abjad here.

The purpose of abjads is to distinguish them from later alphabets, such as Greek, that represent vowels more systematically. A writing system that represents sounds must be either a syllabary or an alphabet, which implies that a system like Aramaic must be either a syllabary (as argued by Gelb) or an incomplete or deficient alphabet (as most other writers have said); however, it is a different type.