Encyclical comes from a Greek term used to indicate letters that princes and magistrates sent to the widest possible number of people in order to make known laws, rules, regulations. etc. The corresponding Latin term was "circularis," which referred to a letter or message intended for extensive circulation. Encyclical today has come to be associated solely with the Church.

Encyclical Letters, the most solemn documents of the ordinary and universal pontifical magisterium, are usually addressed to all the bishops and faithful of the Catholic Church, but frequently are also addressed to include "all people of good will." Encyclical Epistles are addressed to a specific group of bishops - for example those of a specific country or region - and touch upon less important matters.

Encyclicals may deal with doctrinal matters, exhort or call the faithful to public prayer for a specific reason, or be commemorative of an important Church anniversary. They are always signed by the pope, usually in Latin, and are published in the "Acta Apostolicae Sedis" and in individual books in diverse languages.

The official Latin text is prepared by the Secretariat of State and normally five copies of the Latin-language document are signed by the Holy Father. The text, in various languages, is sent to episcopal conferences worldwide through the pontifical representatives.

For many centuries, the office which prepared these documents was called the Chancery of Apostolic Letters. Dating back to the 4th century, the chancery was suppressed by Pope Paul VI with the Motu proprio "Quo aptius" of February 27, 1973. Pope Francis has written 2 encyclicals.

1. Laudato si' Praise be to you - On Care For Our Common Home - May 24, 2015

2 Lumen Fidei (The Light of Faith), June 29, 2013