The movements differ in their views on various issues. These issues include the level of observance, the methodology for interpreting and understanding Jewish law, biblical authorship, textual criticism, and the nature or role of the messiah (or messianic age). Across these movements, there are marked differences in liturgy, especially in the language in which services are conducted, with the more traditional movements emphasizing Hebrew. The sharpest theological division occurs between Orthodox and non-Orthodox Jews who adhere to other denominations, such that the non-Orthodox movements are sometimes referred to collectively as the "liberal denominations" or "progressive streams".