In general, the term Saint refers to someone who is exceptionally virtuous and holy. It can be applied to both the living and the dead and is an acceptable term in most of the world's popular religions. The Saint is held up by the community as an example of how we all should act, and his or her life story is usually recorded for the edification of future generations.
The process of officially recognizing a person as a saint, practiced by some churches, is called canonization.
History of Roman Catholic Saints
Some theologians believe that many people venerated as Saints never actually existed. The polite term for such "Saints" is ahistorical. Sorting out exactly which Saints are ahistorical is difficult, because of the larger difficulty of proving a negative: the absence of independent records of a Saint's existence doesn't prove she or he never existed; indeed there are no specific records of the existence of many people who lived before the 20th century. The Acta Sanctorum (hagiographical work) of the Bollandists forms a major part of the historiography of named Saints.
There are a large number of Catholic Saints with what appear to be pagan names. Most likely they were pagans who converted to Christianity and subsequently became Saints. However, it is possible that some pre-Christian deities (especially in Rome's area) were accidentally adopted as saints. It is thought that some cults were “Christianized” in a fairly direct manner. The basis for this is usually a similarity of names. For example, it is now commonly asserted that Saint Brigid was based on the Celtic goddess Brigid. The goddess was popular long before Christianity reached Ireland. Another possibility is the melding of the actual life of the Saint with myths related to pre-Christian gods and heroes. There are some striking parallels to the events portrayed in the lives of certain saints and fables such as Androcles and the Lion.
In the Roman Catholic church, the title of Saint refers to a person who has been formally canonized (officially recognized) by the Church. This takes place sometime after the person's death and by this definition, never refers to a living person. Formal Canonization is a lengthy process often taking many years, even centuries. The individual is thoroughly investigated by the church and often a number of visions, miracles, or of the holiness and good deeds the person done while on earth in order to be declared a Saint. Also, by this definition there are many people in heaven who are not Saints simply because their lives were not exemplary (though they still went to heaven) and the church does not wish to uphold the individual as an example to be emulated. They are called saints (lowercase 's').
Contrary to popular belief, Saints are not worshiped - this would violate the Commandments - but they are asked for help or to pray for a person. Saints are usually considered to be specific intercessors for specific problems as well. The term Patron Saint usually defines this purpose. Once a person has been declared a Saint, the body of the Saint is considered to be holy. In past centuries, the bones of saints were distributed as holy artifacts. The ring on the finger of Catholic bishops contains the relic of a Saint. In modern times, however, there is a growing trend to show respect for the body of a Saint by leaving it alone and buried.
Calendar of Saints
The calendar of saints is a traditional Christian method of organising a liturgical year on the level of days by associating each day with one or more saints, and referring to the day as the saint's day of that saint. The system arose from the very early Christian custom of annual commemoration of martyrs on the date of their death. As the number of recognized saints increased during Late Antiquity and roughly the first half of the Middle Ages, eventually every day of the year had at least one saint who was commemorated on that date.
Intially, there were two types of saints: martyrs and confessors. Martyrs were people who died in the service of the Lord and confessors were people who died natural deaths. Confessors were not initially considered for saint's days.
This calendar system, when combined with major church festivals and movable and immovable feasts, constructs a very human and personalised yet often localised way of organising the year and identifying dates. It may be compared with the Roman Missal.
Medievalists continue the old tradition of dating by saints' days: their works may appear "dated" as "The Feast of Saint Martin" or "Lammastide". Poets such as John Keats commemorate the importance of The Eve of Saint Agnes.
Many children acquire baptismal or confirmational names from the saint associated with their date of birth, baptism or confirmation, and believing Eastern Orthodox Christians (and in some countries, Roman Catholics) mark the "name day" (namesday) of the saint whose name they bear with special attention, often instead of birthday celebrations.
Various feast days will be "ranked" with various levels of importance. In the Roman Catholic Church, from most to least importance, these are solemnities, feasts, memorials, and optional memorials.