Liturgy (Greek: Λειτουργία) is the customary public worship done by a specific religious group, according to its particular traditions.

The word, sometimes rendered by its English translation "service", may refer to an elaborate formal ritual such as the Eastern Orthodox Divine Liturgy (Greek: Θεία λειτουργία) and Catholic Mass, or a daily activity such as the Muslim salat and Jewish services. As a religious phenomenon, liturgy is a communal response to the sacred through activity reflecting praise, thanksgiving, supplication, or repentance. Ritualization may be associated with life events such as birth, coming of age, marriage and death. It thus forms the basis for establishing a relationship with a divine agency, as well as with other participants in the liturgy. Methods of dress, preparation of food, olication of cosmetics or other hygienic practices are all considered liturgical activities.

The familiar sense of the word is an extension of the technical term in ancient Greek, leitourgia, signifying the often expensive offers of service to the people, and thus to the polis and the state. Through the leitourgia the rich carried a financial burden and were correspondingly rewarded with honours. The leitourgia became both mandatory and honorific, supporting the patron's standing among the elite. The holder of a Hellenic leitourgia was not taxed a specific sum, but entrusted with a particular ritual, which could be performed with greater or lesser magnificence. The chief sphere remained that of civic religion, embodied in the festivals: M.I. Finley notes "in Demosthenes' day there were at least 97 liturgical appointments in Athens for the festivals, rising to 118 in a (quadrennial) Panathenaic year." Eventually, under the Roman Empire, such obligations, known as Monera, devolved into a competitive and ruinously expensive burden that was not avoided^{[clarification needed]} when possible.

Sergei Vasilievich Rachmaninoff (Russian: Серге́й Васи́льевич Рахма́нинов) (Russian pronunciation: [sʲɪrˈɡʲej rɐxˈmanʲɪnəf]; 1 April [O.S. 20 March] 1873 – 28 March 1943) was a Russian composer, pianist, and conductor. Rachmaninoff is widely considered one of the finest pianists of his day and, as a composer, one of the last great representatives of Romanticism in Russian classical music. Early influences of Tchaikovsky, Rimsky-Korsakov, and other Russian composers gave way to a thoroughly personal idiom that included a pronounced lyricism, expressive breadth, structural ingenuity, and a tonal palette of rich, distinctive orchestral colors. The piano is featured prominently in Rachmaninoff's compositional output. He made a point of using his own skills as a performer to explore fully the expressive possibilities of the instrument. Even in his earliest works he revealed a sure grasp of idiomatic piano writing and a striking gift for melody.

Rachmaninoff was born on 1 April [O.S. 20 March] 1873 in Semyonovo, near Great Novgorod, in north-western Russia into a family of the Russian aristocracy, originally of partly Tatar descent, which had been in the service of the Russian tsars since the 16th century. His parents were both amateur pianists. When he was four, his mother gave him casual piano lessons, but it was his paternal grandfather, Arkady Alexandrovich Rachmaninoff, who brought Anna Ornatskaya, a teacher from Saint Petersburg, to teach the 9 year old Sergei in 1882. Ornatskaya remained for two or three years, until the family's house in Semyonovo had to be sold to settle debts and the Rachmaninoffs moved to Saint Petersburg.

John Chrysostom (c. 347–407, Greek: Ἰωάννης ὁ Χρυσόστομος), Archbishop of Constantinople, was an important Early Church Father. He is known for his eloquence in preaching and public speaking, his denunciation of abuse of authority by both ecclesiastical and political leaders, the Divine Liturgy of St. John Chrysostom, and his ascetic sensibilities. After his death in 407 (or, according to some sources, during his life) he was given the Greek epithet chrysostomos, meaning "golden mouthed" in English, and Anglicized to Chrysostom.

The Orthodox and Eastern Catholic Churches honor him as a saint and count him among the Three Holy Hierarchs, together with Basil the Great and Gregory Nazianzus. He is recognized by the Eastern Orthodox Church and the Catholic Church as a saint and as a Doctor of the Church. Churches of the Western tradition, including the Roman Catholic Church, some Anglican provinces, and parts of the Lutheran Church, commemorate him on 13 September. Some Lutheran and many Anglican provinces commemorate him on the traditional Eastern feast day of 27 January. The Coptic Orthodox Church of Alexandria also recognizes John Chrysostom as a saint (with feast days on 16 Thout and 17 Hathor).