The extent of these Jewish languages varied with time and migrations of populations. For more than a millenium, from about 500 B.C.E. to around 650 of the Christian Era, Jewish Aramaic was the language of the overwhelming majority of the Jewish People. Aramaic was the language that dominated the lands of the Fertile Crescent, including all of Babylonia, (Iraq), Syria and Israel. The Jews of Persia (Iran) and Egypt also spoke Jewish Aramaic in addition to the local vernacular. In fact Jewish-Aramaic became so intimate a part of the Jewish people and their religious traditions, that it acquired the status of sanctity alongside the language of the Bible.
Sacred books of Judaism, in addition to the Holy Scriptures, are the Talmud of Jerusalem and the Babylonian Talmud, and the Sefer Ha-Zohar. The Talmuds are the repositories of Jewish Law and the Zohar is the basic work, the foundation of the Kabbalah, the source of Jewish Mysticism. Several of the most significant passages in our Prayer Books are in the Aramaic language, and the two most important documents in Jewish domestic relations; the Marriage Contract, known as the Ketubah, and the Bill of Divorce, known as the Ghet, are not writtin in Hebrew, but in Jewish Aramaic.
After the Moslem-Arab conquests of the middle of the 7th century, Arabic became the dominant language of the lands that were formerly Aramaic-speaking, and extended also along the coast of North Africa to the Atlantic shores. After the Moorish-Arab conquest of Spain in 711, Arabic became the dominant language in the Iberian Peninsula. During this period, from he middle of the seventh century to the end of the thirteenth, Judeo-Arabic was spoken by more Jews than any other language. Almost all of the Jewish philosophers and scientists of that period wrote their scientific and philosophical works in Judeo-Arabic. But poetry was always written in the language of the Book of Psalms and the Prophets.
Around the end of the 14th century, as Judeo-Arabic speakers were declining in number, the major Jewish languages were Djudezmo (=Ladino=Judeo-Spanish), the language of the Jews of Spain, and Yiddish, the language of the Jews of Northern Europe, primarily the ever-growing Jewish population of the Polish Kingdom. The number of Yiddish speakers increased as time went on until in the twentieth century, the Yiddish-speaking Jews outnumbered all other Jewish communities combined. Yiddish was the language spoken by the majority of the Jewish People in 1939, when the total Jewish population worldwide was close to 17 million, and the number of Yiddish speakers exceeded 11 million.