structural:expansion, stylistic:style_transfer, quality:correction
Terminology

Castle is sometimes used as a catch-all term for all kinds of fortifications, and as a result has been misapplied in the technical sense. An example of this is Maiden Castle which, despite the name, is an Iron Age hill fort which had a very different origin and purpose.

Although castle has not become a generic term for a manor house (like château in French and Schloss in German), many manor houses contain castle in their name while having few if any of the architectural characteristics, usually as their owners liked to maintain a link to the past and felt the term castle was a masculine expression of their power. In scholarship the castle, as defined above, is generally accepted as a coherent concept, originating in Europe and later spreading to parts of the Middle East, where they were introduced by European Crusaders. This coherent group shared a common origin, dealt with a particular mode of warfare, and exchanged influences.

In different areas of the world, analogous structures shared features of fortification and other defining characteristics associated with the concept of a castle, though they originated in different periods and circumstances and experienced differing evolutions and influences. For example, shiro in Japan, described as castles by historian Stephen Turnbull, underwent "a completely different developmental history, were built in a completely different way and were designed to withstand attacks of a completely different nature". While European castles built from the late 12th and early 13th century onwards were generally stone, shiro were predominantly timber buildings into the 16th century.

By the 16th century, when Japanese and European cultures met, fortification in Europe had moved beyond castles and relied on innovations such as the Italian trace italienne and star forts.