Encyclical usually refers to a letter sent by the pope to the bishops of the Catholic Church. The term originates from the wide circulation such a letter receives. You can find most encyclicals on the Vatican’s Web site or in print. To cite an encyclical, follow the MLA template of core elements.
If using the version published on the Vatican’s Web site, begin with the name of the pope who wrote the letter, followed by the title of the letter specified on the Web site. In the “Title of container” element, list the The Holy See, followed by the publication date and URL:
In one of his last encyclicals, John Paul II argues that faith and reason are “like two wings on which the human spirit rises to the contemplation of truth.”
John Paul II. “Fides et Ratio.” The Holy See, 14 Sept. 1998, w2.vatican.va/content/john-paul-ii/en/encyclicals/documents/hf_jp-ii_enc_14091998_fides-et-ratio.html.
If you are consulting a book, list all the core elements that apply to the published version in your works-cited-list entry. Your parenthetical reference should include a page number if you quote the letter:
In one of his last encyclicals, John Paul II argues that faith and reason are “like two wings on which the human spirit rises to the contemplation of truth” (3).
John Paul II. Encyclical Letter “Fides et Ratio” (Faith and Reason): Of the Supreme Pontiff John Paul II, to the Bishops of the Catholic Church on the Relationship between Faith and Reason. St. Paul’s Press, 1998.