opus [Lat.,=work], in music, term used in cataloging a composer's works, designating either a single composition or a group published together or considered a unit. Opus numbers assigned by the composer are of greater value than those assigned by the publisher. Beethoven was the first composer whose use of opus numbers was consistent enough to be of value.

Opus Dei [Lat.,=work of God], Roman Catholic organization, particularly influential in Spain, officially the Prelature of the Holy Cross and Opus Dei. Opus Dei was founded in 1928 by a wealthy lawyer turned priest, José María Escrivá de Balaguer y Albás, who objected to the liberal, secular atmosphere at the Univ. of Madrid. As a Catholic institution, it emphasizes that ordinary Christians can achieve holiness and change society for the better through how they live their everyday lives. Opus Dei gained national importance in Spain after the civil war, when it received support from goverment of Francisco Franco. In the 1950s and 60s it replaced the Falange as the most important conservative political and religious force in Spain. Its influence there, however, has waned since the early 1970s.

Receiving increased support from the Vatican since the late 1970s, the organization has grown to more than 85,000 members in more than 80 countries. In 1950 the Vatican recognized it as a secular institute; in 1982 it was given the status of "personal prelature." Its membership is now, therefore, considered a separate diocese with its own bishop.

Believing that a Catholic can lead a holy life without taking religious vows, lay members pledge to serve God in worldly vocations; roughly a third of the members live communally and celibately in Opus Dei centers. The movement seeks to promote traditional Catholic values and teaching and to oppose liberalism and immorality, and is noted for its emphasis on preaching to government officials, professionals, intellectuals, and business executives. Opus Dei has been controversial among some Catholics because of its secretive nature, its emphasis on discipline, its conservatism, and its historical association with the Franco regime in Spain. This controversy became pronounced in 1992 when the Vatican, under John Paul II, beatified Escrivá; Escrivá was canonized in 2002.

Opus Dei(Latin; “work of God”)

Roman Catholic lay and clerical organization whose actions and beliefs have been both criticized and praised. Its members seek personal Christian perfection, strive to implement Christian ideals in their chosen occupations, and promote Christian values to society as a whole. Opus Dei, in full Prelature of the Holy Cross and Opus Dei, was founded in 1928 in Spain by Josemaría Escrivá de Balaguer y Albá (canonzied in 2002). It is theologically conservative and accepts the teaching authority of the church without question. It was granted special status as the first and only personal prelature in the church by Pope John Paul II in 1982 and has established numerous vocational schools and universities. It is also highly controversial, accused of secrecy, using cult-like recruiting practices, and having grand political ambitions. There are separate organizations for men and women, which, since 1982, have been headed by a prelate elected by its members. At the beginning of the 20th century priests constituted only a tiny percentage of the organization, numbering roughly 1,600 of the nearly 84,000 members living in 80 countries.

Learn more about Opus Dei with a free trial on Britannica.com.