The term chapel usually refers to a place of prayer and worship that is attached to a larger, often nonreligious institution or that is considered an extension of a primary religious institution. It may be part of a larger structure or complex, such as a college, hospital, palace, prison, funeral home, church, synagogue or mosque, located on board a military or commercial ship, or it may be an entirely free-standing building, sometimes with its own grounds. Chapel has also referred to independent or nonconformist places of worship in Great Britain—outside the established church.
Until the Protestant Reformation, a chapel denoted a place of worship that was either at a secondary location that was not the main responsibility of the local parish priest, or that belonged to a person or institution. The earliest Christian places of worship are now often referred to as chapels, as they were not dedicated buildings but rather a dedicated chamber within a building. Most larger churches had one or more secondary altars, which if they occupied a distinct space, would often be called a chapel. In Russian Orthodox tradition, the chapels were built underneath city gates, where most people could visit them. The most famous example is the Iberian Chapel.
Although chapels frequently refer to Christian places of worship, they are also commonly found in Jewish synagogues and do not necessarily connote a specific denomination. In England—where the Church of England is established by law—non-denominational or inter-faith chapels in such institutions may nonetheless be consecrated by the local Anglican bishop. Non-denominational chapels are commonly encountered as part of a non-religious institution such as a hospital, airport, university or prison. Many military installations have chapels for the use of military personnel, normally under the leadership of a military chaplain.
The earliest Christian places of worship were not dedicated buildings but rather a dedicated chamber within a building, such as a room in an individual's home. Here one or two people could pray without being part of a communion/congregation. People who like to use chapels may find it peaceful and relaxing to be away from the stress of life, without other people moving around them.
The word, chapel, like the associated word, chaplain, is ultimately derived from Latin. More specifically, the word "chapel" is derived from a relic of Saint Martin of Tours: traditional stories about Martin relate that while he was still a soldier, he cut his military cloak in half to give part to a beggar in need. The other half he wore over his shoulders as a "small cape" (Latin: capella). The beggar, the stories claim, was Christ in disguise, and Martin experienced a conversion of heart, becoming first a monk, then abbot, then bishop. This cape came into the possession of the Frankish kings, and they kept the relic with them as they did battle. The tent which kept the cape was called the capella and the priests who said daily Mass in the tent were known as the capellani. From these words, via Old French, we get the names "chapel" and "chaplain".
The word also appears in the Irish language in the Middle Ages, as Welsh people came with the Norman and Old English invaders to the island of Ireland. While the traditional Irish word for church was eaglais (derived from ecclesia), a new word, séipéal (from cappella), came into usage.
In British history, "chapel" or "meeting house", was formerly the standard designation for church buildings belonging to independent or Nonconformist religious societies and their members. It was a word particularly associated with the pre-eminence of independent religious practice in rural regions of England and Wales, the northern industrial towns of the late 18th and 19th centuries, and centres of population close to but outside the City of London. As a result, "chapel" is sometimes used as an adjective in the UK to describe the members of such churches ("I'm Chapel.").
A proprietary chapel is one that originally belonged to a private person. In the 19th century they were common, often being built to cope with urbanisation. Frequently they were set up by evangelical philanthropists with a vision of spreading Christianity in cities whose needs could no longer be met by the parishes. Some functioned more privately, with a wealthy person building a chapel so they could invite their favorite preachers. They are anomalies in the English ecclesiastical law, having no parish area, but being able to have an Anglican clergyman licensed there. Historically many Anglican Churches were Proprietary Chapels. Over the years they have often been converted into normal Parishes.
While the usage of the word "chapel" is not exclusively limited to Christian terminology, it is most often found in that context. Nonetheless, the word's meaning can vary by denomination, and non-denominational chapels (sometimes called "meditation rooms") can be found in many hospitals, airports, and even the United Nations headquarters. Chapels can also be found for the worship of Judaism.
The word chapel is in particularly common usage in the United Kingdom, and even more so in Wales, for Nonconformist places of worship; and in Scotland and Ireland for Roman Catholic churches. In the UK, due to the rise in Nonconformist chapels throughout the late eighteenth and early nineteenth centuries, by the time of the 1851 census, more people attended the independent chapels than attended the state's Anglican churches.
In Roman Catholic Church canon law, a chapel, technically called an "oratory" is a building or part thereof dedicated to the celebration of services, particularly the Mass, which is not a parish church. This may be a private chapel, for the use of one person or a select group (a bishop's private chapel, or the chapel of a convent, for instance); a semi-public oratory, which is partially available to the general public (a seminary chapel that welcomes visitors to services, for instance); or a public oratory (for instance, a hospital or university chapel).
Chapels that are built as part of a larger church are holy areas set aside for some specific use or purpose: for instance, many cathedrals and large churches have a "Lady Chapel" in the apse, dedicated to the Virgin Mary; parish churches may have such a "Lady Chapel" in a side aisle or a "Chapel of Reservation" or "Blessed Sacrament Chapel" where the consecrated bread of the Eucharist is kept in reserve between services, for the purpose of taking Holy Communion to the sick and housebound and, in some Christian traditions, for devotional purposes.
Common uses of the word chapel today include:
- Side-chapel or side chapel – a chapel within a cathedral or larger church building.
- Lady chapel – these are really a form of side chapel, but have been included separately as they are extremely prevalent in the Roman Catholic Church and the Anglican Communion. They are dedicated to the veneration of the Blessed Virgin Mary.
- Ambassador's Chapel – originally created to allow ambassadors from Catholic countries to worship whilst on duty in Protestant countries.
- Bishop's Chapel – in Anglican and Roman Catholic canon law, Bishops have the right to have a chapel in their own home, even when travelling (such personal chapels may be granted only as a favor to other priests)
- Chapel of rest – not a place of worship as such, but a comfortably decorated room in a funeral directors premises, where family and friends can view the deceased before the funeral.
- Chapel of ease – constructed in large parishes to allow parishioners easy access to a church or chapel.
- Multifaith chapel – found within hospitals, airports and universities, etc.; often converted from being exclusively Christian.
- Summer chapel – A small church in a resort area that functions only during the summer when vacationers are present.
- Wayside chapel or Country chapel – Small chapels in the countryside
- Wedding chapel (U.S.) – space used for weddings 
The first airport chapel was created in 1951 in Boston for airport workers but grew to include travelers. It was originally Catholic but chapels today are often multifaith.
St. Dimitrius Chapel on the beach of Olympiaki Akti, Greece
Methodist Chapel in Kent, Ohio, United States
Littlejohn Memorial Chapel, an example of a school chapel at Scotch College, Melbourne
Processional Chapel in Varennes, Quebec
Turvey Abbey, chapel interior
Open Chapel in Steinfurt, Germany
Eton College Chapel in Eton College, England
Saint Emeric chapel in Zichyújfalu
Avon Old Farms School - the chapel
Cappella degli Scrovegni in Padua.
Chapel at Callaway Gardens
Memorial Chapel at Lake Junaluska
- "Muslim prayers welcome at Pentagon chapel". Retrieved 3 March 2016.
- Catholic Encyclopedia
- Wakeling, Christopher (August 2016). "Nonconformist Places of Worship: Introductions to Heritage Assets". Historic England. Retrieved 28 March 2017.
- Jones, Anthony (1996). Welsh Chapels. National Museum Wales. ISBN 9780750911627. Retrieved 28 March 2017.
- Hewson, Chris (1 January 2010). "Multi-faith Spaces: Symptoms and Agents of Religious and Social Change". University of Manchester. Retrieved 14 September 2012.
- "Royal Army Chaplains' Department". www.army.mod.uk. The British Army. Retrieved 28 March 2017.
- "Archived copy". Archived from the original on 9 May 2008. Retrieved 15 October 2008.
- Cadge, Wendy (3 January 2018). "As you travel, pause and take a look at airport chapels". The Conversation (website). Retrieved 12 January 2018.