The ancient Aramaic alphabet is adapted from the Phoenician alphabet and became distinctive from it by the 8th century BCE. It was used to write the Aramaic language and had displaced the Paleo-Hebrew alphabet, itself a derivative of the Phoenician alphabet, for the writing of Hebrew. The letters all represent consonants, some of which are also used as matres lectionis to 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. That is primarily from the widespread usage of the Aramaic language as both a lingua franca and the official language of the Neo-Assyrian and Neo-Babylonian Empires, and their 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. The Aramaic alphabet was an ancestor to the Nabataean alphabet and the later Arabic alphabet.
Writing systems (like the Aramaic one) that indicate consonants but do not indicate most vowels other than by means of matres lectionis or added diacritical signs, have been called abjads by Peter T. Daniels to distinguish them from alphabets, such as the Greek alphabet, which represent vowels more systematically. The term was coined to avoid the notion that a writing system that represents sounds must be either a syllabary or an alphabet, which would imply that a system like Aramaic must be either a syllabary (as argued by Ignace Gelb) or an incomplete or deficient alphabet (as most other writers have said). Rather, it is a different type....LESS