Guttural R
Many Jewish immigrants to Israel spoke a variety of Arabic in their countries of origin and pronounced the Hebrew rhotic as an alveolar tap , similar to Arabic '. Gradually, many of them began pronouncing their Hebrew rhotic as a voiced uvular fricative , a sound similar or (depending on the Arabic dialect) identical to Arabic '. However, in modern Sephardic and Mizrahi poetry and folk music an alveolar rhotic continues to be used.
Medieval Hebrew
Medieval Hebrew was a literary and liturgical language that existed between the 4th and 18th century. It was not commonly used as a spoken language, but mainly in written form by rabbis, scholars and poets. Medieval Hebrew had many features that distinguished it from older forms of Hebrew. These affected grammar, syntax, sentence structure, and also included a wide variety of new lexical items, which were either based on older forms or borrowed from other languages, especially Aramaic, Greek and Latin.
In the Golden age of Jewish culture in the Iberian Peninsula, important work was done by grammarians in explaining the grammar and vocabulary of Biblical Hebrew; much of this was based on the work of the grammarians of Classical Arabic. Important Hebrew grammarians were Judah ben David Hayyuj and Jonah ibn Janah. A great deal of poetry was written, by poets such as Dunash ben Labrat, Solomon ibn Gabirol, Judah ha-Levi, David Hakohen and the two Ibn Ezras, in a "purified" Hebrew based on the work of these grammarians, and in Arabic quantitative metres (see piyyut). This literary Hebrew was later used by Italian Jewish poets.