Orthodox Judaism is the approach to religious Judaism which subscribes to a tradition of mass revelation and adheres to the interpretation and application of the laws and ethics of the Torah as legislated in the Talmudic texts by the Tannaim and Amoraim. Orthodox Judaism includes movements such as Modern Orthodox Judaism (אורתודוקסיה מודרנית) and Ultra-Orthodox or Haredi Judaism (יהדות חרדית).
As of 2001, Orthodox Jews and Jews affiliated with an Orthodox synagogue accounted for approximately 50% of British Jews (150,000), 26.5% of Israeli Jews (1,500,000), and 13% of American Jews (529,000). Among those affiliated to a synagogue body, Orthodox Jews represent 70% of British Jewry, and 27% of American Jewry.
Orthodoxy is not one single movement or school of thought. There is no single rabbinical body to which all rabbis are expected to belong, or any one organization representing member congregations.
In the 20th century, a segment of the Orthodox population (as represented by the World Agudath Israel movement) disagreed with Modern Orthodoxy and took a stricter approach. Such rabbis viewed innovations and modifications within Jewish law and customs with extreme care and caution. This form of Judaism may be referred to as Haredi Judaism or "Ultra-Orthodox Judaism".
According to the New Jersey Press Association, several media entities refrain from using the term "ultra-Orthodox", including the Religion Newswriters Association; JTA, the global Jewish news service; and the Star-Ledger, New Jersey’s largest daily newspaper. Several local Jewish papers, including New York's Jewish Week and Philadelphia's Jewish Exponent have also dropped use of the term. According to Shammai Engelmayer, spiritual leader of Temple Israel Community Center in Cliffside Park and former executive editor of Jewish Week, this leaves "Orthodox" as "an umbrella term that designates a very widely disparate group of people very loosely tied together by some core beliefs."