Semitic languages
The similarity of the Hebrew, Arabic and Aramaic languages was accepted by Jewish and Islamic scholars since medieval times. The languages were familiar to Western European scholars due to historical contact with neighbouring Near Eastern countries and through Biblical studies, and a comparative analysis of Hebrew, Arabic, and Aramaic was published in Latin in 1538 by Guillaume Postel. Almost two centuries later, Hiob Ludolf described the similarities between these three languages and the Ethiopian Semitic languages. However, neither scholar named this grouping as "Semitic".
Semitic languages
The West Semitic languages significantly reshaped the system. The most substantial changes occurred in the Central Semitic languages (the ancestors of modern Hebrew, Arabic and Aramaic). Essentially, the old prefix-conjugated jussive and/or preterite became a new non-past (or imperfect), while the stative became a new past (or perfect), and the old prefix-conjugated non-past (or imperfect) with gemination was discarded. New suffixes were used to mark different moods in the non-past, e.g. Classical Arabic "-u" (indicative), "-a" (subjunctive), vs no suffix (jussive). (It is not generally agreed whether the systems of the various Semitic languages are better interpreted in terms of tense, i.e. past vs. non-past, or aspect, i.e. perfect vs. imperfect.) A special feature in classical Hebrew is the waw-consecutive, prefixing a verb form with the letter waw in order to change its tense or aspect. The South Semitic languages show a system somewhere between the East and Central Semitic languages.