A cathedral is a Christian church that contains the seat of a bishop. It is a religious building for worship, specifically of a denomination with an episcopal hierarchy, such as the Roman Catholic, Anglican, Orthodox and some Lutheran churches, which serves as a bishop's seat, and thus as the central church of a diocese.
There are certain deviations on the use of the term "cathedral"; for example, some pre-Reformation cathedrals in Scotland now within the Church of Scotland still retain the term cathedral, despite the Church's Presbyterian polity which does not have bishops. As cathedrals are often particularly impressive edifices, the term is often used incorrectly as a designation for any large important church.
The term "cathedral" is not officially used in Eastern Orthodoxy, the church of a bishop being known as "the great church", though cathedral is commonly used in English translations. The Oriental Orthodox Churches similarly do not have cathedrals as such, however some major churches like Saint Mark's Coptic Orthodox Cathedral in Cairo are called cathedrals.
Several cathedrals in Europe, such as Strasbourg, and in England at York, Lincoln and Southwell, are referred to as Minster (German: Münster) churches, from Latin monasterium, because the establishments were served by canons living in community or may have been an abbey, prior to the Reformation. The other kind of great church in Western Europe is the abbey.

Designation
In the Canon law of the Catholic Church the relationship of the bishop to his cathedral is often compared to the relationship of a pastor to the parochial church. Both are pastors over an area (the diocese for the bishop and the parish for the pastor) and both are rectors over a building (the cathedral for the bishop and the parish church for the pastor). In view of this, canon lawyers often extend the metaphor and speak of the cathedral church as the one church of the diocese, and all others are deemed chapels in their relation to it.
Cathedral churches may have different degrees of dignity:
-A parish church that was formerly a cathedral is known as a proto-cathedral.
-A parish church that is temporarily serving as the cathedral or co-cathedral of a diocese is known as a pro-cathedral.
-A church that serves as an additional cathedral of a diocesan bishop is known as a co-cathedral.
-The church of a diocesan bishop is known as a cathedral.
-A church to which the other diocesan cathedral churches of a province are suffragan is a metropolitan cathedral.
-A church under which are ranged metropolitical churches and their provinces is a primatial cathedral.
-A church to which primatial, metropolitical, and cathedral churches alike owe allegiance is a patriarchal cathedral.
The title of "primate" was occasionally conferred on metropolitan bishops of sees of great dignity or importance, such as Canterbury, York and Rouen, whose cathedral churches remained simply metropolitical.
Lyon, where the cathedral church is still known as La Primatiale, and Lund in Sweden, may be cited as instances of churches which were really primatial. Lyon had the archbishops of Sens and Paris and their provincial dioceses subject to it until the French Revolution, and Lund had the archbishop of Uppsala and his province subject to it.
As with the title of primate, so also that of "patriarch" has been conferred on sees such as Venice and Lisbon, the cathedral churches of which are patriarchal in name alone. The Basilica di San Giovanni in Laterano, the cathedral church of Rome, alone in Western Europe possesses a patriarchal character among Roman Catholics, since the Pope is the Patriarch of the Latin Rite church. However, in February of 2006 Pope Benedict XVI ceased the use of the title "Patriarch of the West".
The removal of a bishop's cathedra from a church deprives that church of its cathedral dignity, although often the name clings in common speech, as for example at Antwerp, which was deprived of its bishop at the French Revolution. Technically, such a church is a proto-cathedral.

The Cathedral building
Although a cathedral may be amongst the grandest of churches in the diocese (and country), especially those dating from Medieval and Renaissance times, size and grandeur have never been requirements and (especially in modern times, where functionality is the foremost consideration) a cathedral church may be a modest structure. Early Celtic and Saxon cathedrals, for example, tended to be of diminutive size, as is the Byzantine so-called Little Metropole Cathedral of Athens.
The plan of a cathedral generally takes the form of a cross which has both symbolic meaning and is functional in terms of church worship, allowing space for clergy, choir, chapels, processions a pipe organ and other activities and objects associated with cathedral tradition.
A cathedral, in common with other Christian churches has an altar or table upon which the Eucharist is laid, a lectern for reading the Bible and a pulpit from which the sermon is traditionally preached. Cathedrals also have a baptismal font for the traditional rite of washing that marks the acceptance of a new Christian, (most usually an infant) into the Church. Particularly in Italy, baptism may take place in a separate building for that purpose. Within the church, an area, usually to the eastern end, is set aside for the ceremonial seats of the dignatories of the church, as well as the choir.
Cathedrals of monastic foundation, and some of secular clergy have square cloisters which traditionally provided an open area where secular activities took place protected from wind and rain. Some cathedrals also have a chapter house where the chapter could meet. In England, where these buildings have survived, they are often octagonal. A cathedral may front onto the main square of a town, as in Florence, or it may be set in a walled close as at Canterbury. There may be a number of associated monastic or clergy buildings, a bishop's palace and often a school to educate the choristers.

In English a palace is the home of a head of state or other high-ranking public figure. In some countries, such as Italy, the term is also applied to some private mansions. Many palaces are now put to other uses such as parliaments or museums. The word is also sometimes used to describe a lavish public building which does not house a public figure; this use is intended to convey that the building is a "people's palace", where a sort of civic consciousness resides.
Historians apply the term "palace" anachronistically, to label the complex structures of Minoan Knossos, or the Mycenaean palace societies, or the 4th century incompletely-Hellenize palace system of Philip of Macedon's Vergina— or palaces outside the European world entirely.

Etymology
Queluz National Palace
The word "palace" comes from the name of one of the seven hills of Rome, the Palatine Hill. The original 'palaces' on the Palatine Hill were the seat of the imperial power, while the capitol on the Capitoline Hill was the seat of the senate and the religious nucleus of Rome. Long after the city grew to the seven hills the Palatine remained a desirable residential area. Augustus Caesar lived there in a purposely modest house only set apart from his neighbors by the two laurel trees planted to flank the front door as a sign of triumph granted by the Senate. His descendants, especially Nero, with his "Golden House" enlarged the house and grounds over and over until it took up the hill top. The word Palatium came to mean the residence of the emperor rather than the neighborhood on top of the hill.

Palaces elsewhere
"Palace" meaning "government" can be recognized in a remark of Paul the Deacon, writing ca 790 and describing events of the 660s: "When Grimuald set out for Beneventum, he intrusted his palace to Lupus" (Historia gentis Langobardorum, V.xvii). At the same time Charlemagne was consciously reviving the Roman expression in his "palace" at Aachen, of which only his chapel remains. In the 9th century the "palace" indicated the housing of the government too, and the constantly-travelling Charlemagne built fourteen. In the early Middle Ages, the Palas remained the seat of government in some German cities. In the Holy Roman Empire the powerful independent Electors came to be housed in palaces (Paläste) This has been used as evidence that power was widely distributed in the Empire, as in more centralized monarchies, only one supreme monarch would be allowed to call their home a palace.
In France there has been a clear distinction between a château and a palais. The palace has always been urban, like the Palais de la Cité in Paris (above), which was the royal palace of France and is now the supreme court of justice of France, or the palace of the Popes at Avignon (illustration, left).
The château, by contrast, has always been in rural settings, supported by its demesne, even when it was no longer actually fortified. Speakers of English think of the "Palace of Versailles" because it was the residence of the king of France, and the king was the source of power, though the building has always remained the Château de Versailles for the French, and the seat of government under the ancien regime remained the Palais du Louvre. The Louvre had begun as a fortified Château du Louvre on the edge of Paris, but as the seat of government and shorn of its fortified architecture and then completely surrounded by the city, it developed into the Palais du Louvre.
In Italy, where localized regimes lasted to the 19th century, many a small former capital displays its Palazzo Ducale, the seat of government. In Florence and other strong communal governments, the seat of government was the Palazzo della Signoria until in Florence the Medici were made Grand Dukes of Tuscany. Then, when the power center shifted to their residence in Palazzo Pitti, the old center of power began to be called the Palazzo Vecchio.
But indeed, in some Italian cities, it is not uncommon to find many "palaces," including some comparatively humble mansions, each built by one of the principal noble families. Each family's palazzo was a hive that contained all the family members, though it might not always show a grand architectural public front. In the 20th century palazzo in Italian came to apply to any large fine apartment building.
In England, by tacit agreement, there have been no "palaces" other than those used as official residences by royalty and certain bishops. Thus the Palace of Beaulieu gained its name precisely when Thomas Boleyn sold it to Henry VIII in 1517; previously it had been known as Walkfares. But like several other palaces, the name stuck even once the royal connection ended. Although the Palace of Blenheim (illustration, left) was never a royal residence, the name was part of the extraordinary honour when the house was given by a grateful nation to a great general. (Along with several royal and episcopal palaces in the countryside, Blenheim does demonstrate that "palace" has no specific urban connotations in English.)
As on the continent, these royal and episcopal palaces were not merely residences; the clerks who administered the realm or the diocese labored there as well. (To this day many bishops' palaces house both their family apartments and their official offices.) However, unlike the "Palais du Justice" which is often encountered in the French-speaking world, modern British public administration buildings are never called "palaces"; although the formal name for the "Houses of Parliament" is the Palace of Westminster, this reflects Westminster's former role as a royal residence and centre of administration.
In more recent years, the word has been used in a more informal sense for other large, impressive buildings, such as The Crystal Palace of 1851 (an immensely large, glazed hall erected for the Great Exhibition) and modern arenas-convention centres like Alexandra Palace (which is no more a palace than Madison Square Garden is a garden).

A castle is a defensive structure seen as one of the main symbols of the Middle Ages. The term has a history of scholarly debate surrounding its exact meaning, but it is usually regarded as being distinct from the general terms fort or fortress in that it describes a building which serves as a residence and commands a specific territory.
Roman forts and hill forts were the main antecedents of castles in Europe, which emerged in the 9th century in Carolingian France. The advent of cannon and gunpowder changed the needs of warfare in Europe, limiting the effectiveness of the castle and leading to the rise of the fort.

Definition
Castle comes from the Latin word castellum meaning "fortress". This is a diminutive of the word castrum, which means "fortified place". The word "castle" (castel) was introduced into English shortly before the Norman Conquest to denote this type of fortress, then new to England, brought in by the Norman knights. In Spain, a fortified dwelling on a height for the administering authority retains its Moorish name of alcázar, whilst shiro also figure prominently in Japanese history, where the feudal daimyō inhabited them.
A French castle is a château-fort, for in French a simple château connotes a grand country house at the heart of an estate, with non-military, purely residential function. When European castles were opened up and expanded into pleasure dwellings and power houses from the late 15th century, their "castle" designations, relics of the feudal age, often remained attached to the dwelling, resulting in many non-military castles and châteaux.
In Germany there are two names for what would be called a castle in English, Burg and Schloss. A Burg is a medieval structure of military significance, while a Schloss was built after the Middle Ages as a palace and not for defensive purposes. However, these are not usually palaces in the French style, but instead are styled on medieval mountain castles and fairytale notions, and from all appearances are often castles to an English speaker.
In Celtic countries, Caer or castell (Welsh), dún and caisleán (Irish), dùn and caisteal (Scots Gaelic) are used.
In spite of the generally accepted definition, the word "castle" is sometimes used to mean a citadel (such as the castles of Badajoz and Burgos) or small detached forts d'arrêt in modern times and, traditionally, in Britain it has also been used to refer to prehistoric earthworks (e.g. Maiden Castle). The use of the Spanish equivalent castillo can be equally misleading, as it can refer to true castles and forts (eg. Castillo de San Marcos); terms such as Fortaleza ("fortress") are in similar situations.

Construction
Castles were constructed of wood, stone and also brick. A large number of contemporary accounts have survived that explain how castles were built. A large skilled workforce was needed to construct castles, including ditch diggers, stonecutters, masons, carpenters, and engineers. Medieval machines and inventions, such as the treadwheel crane, became indispensable during construction, and techniques of building wooden scaffolding were improved upon from Antiquity. Nevertheless, castles could take many years to complete, although the time needed depended greatly from type, location, resources, time period, construction materials, etc.
Finding stone was the first concern of medieval builders, and a major preoccupation was to have quarries close at hand. There are famous examples of some castles where stone was quarried on site, such as Chinon, Château de Coucy and Château Gaillard. Yet even without the usual costs of transport, it is estimated that as many as 800 stonemasons would have been used in building Château de Coucy in the early 13th century, as well as perhaps 800 other craftsmen. Beaumaris Castle in Wales, has surviving records from 1295–96 which describe 200 quarrymen, 400 stonemasons and as many as 2000 minor workmen. Castles, not surprisingly were expensive to build, considering workers and materials. For example costs for Beaumaris, only part of a bigger castle program was £14,500 (roughly $20–30 million in today's money).
In some cases, transporting stone over large distances was altogether impractical, and in the Low countries, a lack of good building stone meant that castles were generally brick. Brick castles were predominant in Scandinavia and the Baltic.

Baroque
Fountain
Amphitheatre
Atrium
Tower