Historical: Yiddish
Modern: Local languages, primarily: English, Hebrew, Russian
primarily Judaism
Sephardi Jews, Mizrahi Jews, and other Jewish ethnic divisions.
Ashkenazi Jews, also known as Ashkenazic Jews or Ashkenazim (Hebrew: אַשְׁכֲּנָזִים, pronounced [ˌaʃkəˈnazim], singular: [ˌaʃkəˈnazi]; also יְהוּדֵי אַשְׁכֲּנָז, Yehudei Ashkenaz, "the Jews of Ashkenaz"), are the Jews descended from the medieval Jewish communities along the Rhine in Germany from Alsace in the south to the Rhineland in the north. Ashkenaz is the medieval Hebrew name for this region and thus for Germany. Thus, Ashkenazim or Ashkenazi Jews are literally "German Jews." Later, Jews from Western and Central Europe came to be called "Ashkenaz" because the main centers of Jewish learning were located in Germany. (See Usage of the name for the term's etymology.) Ashkenaz is also a Japhetic patriarch in the Table of Nations (Genesis 10).
Many Ashkenazi Jews later migrated, largely eastward, forming communities in non German-speaking areas, including Hungary, Poland, Belarus, Lithuania, Russia, Ukraine, Eastern Europe, and elsewhere between the 11th and 19th centuries. With them, they took and diversified Yiddish, a basically Germanic language with Hebrew influence (see Jewish language). It had developed in medieval times as the lingua franca among Ashkenazi Jews. The Jewish communities of three cities along the Rhine: Speyer, Worms and Mainz, created the SHUM league (SHUM after the first Hebrew letters of Spira, Warmatia and Magentza). The SHUM-cities are considered the cradle of the distinct Ashkenazi culture and liturgy.
Although in the 11th century, they comprised only 3 percent of the world's Jewish population, at their peak in 1931, Ashkenazi Jews accounted for 92 percent of the world's Jews. Today they make up approximately 80 percent of Jews worldwide.[5] Most Jewish communities with extended histories in Europe are Ashkenazim, with the exception of those associated with the Mediterranean region. The majority of the Jews who migrated from Europe to other continents in the past two centuries are Ashkenazim, Eastern Ashkenazim in particular. This is especially true in the United States, where most of the 5.3 million American Jewish population[6] is Ashkenazi, representing the world's single largest concentration of Ashkenazim.
The exact definition of Jewishness is not universally agreed upon—neither by religious scholars (especially across different denominations); nor in the context of politics (as applied to those who wish to make Aliyah); nor even in the conventional, everyday sense where 'Jewishness' may be loosely understood by the casual observer as encompassing both religious and secular Jews, or religious Jews alone. This makes it especially difficult to define who is an Ashkenazi Jew. The people have been defined differently from religious, cultural, or ethnic perspectives.
Since the overwhelming majority of Ashkenazi Jews no longer live in Eastern Europe, the isolation that once favored a distinct religious tradition and culture has vanished. Furthermore, the word Ashkenazi is being used in non-traditional ways, especially in Israel. By conservative and orthodox philosophies, a person can only be considered a Jew if his or her mother was Jewish (meaning, more specifically, either matrilineal descent from a female believed to be present at Mt. Sinai when the ten commandments were given, or else descent from a female who was converted to Judaism before the birth of her children), or if he or she has personally converted to Judaism. This means that a person can be Ashkenazi but not considered a Jew by some of those within the Jewish communities, making the term "Ashkenazi" more applicable as broad ethnicity which evolved from the practice of Judaism in Europe.
Religious Jews have Minhagim, customs, in addition to Halakha, or religious law, and different interpretations of law. Different groups of religious Jews in different geographic areas historically adopted different customs and interpretations. On certain issues, Orthodox Jews are required to follow the customs of their ancestors, and do not believe they have the option of picking and choosing. Therefore, observant Jews at times find it important for religious reasons to ascertain who their household's religious ancestors are in order to know what customs their household should follow. These times include, for example, when two Jews of different ethnic background marry, when a non-Jew converts to Judaism and determines what customs to follow for the first time, or when a lapsed or less observant Jew returns to traditional Judaism and must determine what was done in his or her family's past. In this sense, "Ashkenazic" refers both to a family ancestry and to a body of customs binding on Jews of that ancestry.
In a religious sense, an Ashkenazi Jew is any Jew whose family tradition and ritual follows Ashkenazi practice. Until the Ashkenazi community first began to develop in the Early Middle Ages, the centers of Jewish religious authority were in the Islamic world, at Baghdad and in Islamic Spain. Ashkenaz (Germany) was so distant geographically that it developed a minhag of its own. Ashkenazi Hebrew came to be pronounced in ways distinct from other forms of Hebrew.
In this respect, the counterpart of Ashkenazi is Sephardic, since most non-Ashkenazi Orthodox Jews follow Sephardic rabbinical authorities, whether or not they are ethnically Sephardic. By tradition, a Sephardic or Mizrahi woman who marries into an Orthodox or Haredi Ashkenazi Jewish family raises her children to be Ashkenazi Jews; conversely an Ashkenazi woman who marries a Sephardi or Mizrahi man is expected to take on Sephardic practice and the children inherit a Sephardic identity, though in practice many families compromise. A convert generally follows the practice of the beth din that converted him or her.
With the integration of Jews from around the world in Israel, North America, and other places, the religious definition of an Ashkenazi Jew is blurring, especially outside Orthodox Judaism. Many Sephardic and Mizrahi Jews have joined liberal movements that originally developed within Ashkenazi Judaism. In recent decades, the congregations which they have joined have often embraced them, and absorbed new traditions into their minhag. Rabbis and cantors in most non-Orthodox movements study Hebrew in Israel, where they learn Sephardic rather than Ashkenazi Hebrew pronunciation. Ashkenazi congregations are adopting Sephardic or modern Israeli melodies for many prayers and traditional songs. Since the middle of the 20th century, there has been a gradual syncretism and fusion of traditions. This is affecting the minhag of all but the most traditional congregations.