Pia unio

Associations of the faithful are groups of Catholics, clerics or laity or both together, who according to the Code of Canon Law jointly foster a more perfect life or promote public worship or Christian teaching, or who devote themselves to other works of the apostolate. They are not necessarily established or even praised or recommended by the Church authorities.

A 20th-century resurgence of interest in lay societies culminated in the Second Vatican Council, but lay ecclesial societies have long existed in forms such as sodalities (defined in the 1917 Code of Canon Law as associations of the faithful constituted as an organic body),confraternities (similarly defined as sodalities established for the promotion of public worship),medieval communes, and guilds.

Pope John Paul II's apostolic exhortation Christifideles laici of 30 December 1988 spoke of "the flourishing of groups, associations and spiritual movements as well as a lay commitment in the life of the Church" in the years following the Second Vatican Council, "resulting in the birth and spread of a multiplicity of group forms: associations, groups, communities, movements".

A Pastoral Note of the Italian Episcopal Conference issued on 29 April 1993 defined three of these terms as follows:

However, it added that these terms are often applied quite loosely. As an example, the Community of Sant'Egidio, which calls itself a community, is also described as a movement, and is listed as an association in the Directory of International Associations of the Faithful.

Under the 1917 Code of Canon Law, replaced in 1983 by a revised Code, associations of the faithful were called piae uniones ("pious unions").

For a list of the officially approved associations of the faithful that exist on an international level, see Directory of International Associations of the Faithful. Approval for those that exist on a national level can be obtained from the country's episcopal conference, while it is for the local bishop to grant approval to those that exist only at diocesan level.

...
Wikipedia