A capital is the area of a country regarded as enjoying primary status; it is almost always the city which physically encompasses the offices and meeting places of the seat of government and fixed by law, but there are a number of exceptions. Alternate terms include capital city and political capital; the latter phrase has a second meaning based on an alternative sense of "capital".

The word capital is derived from the Latin caput meaning "head," and the related term Capitol refers to the building where government business is chiefly conducted.

Seats of government in major sub-state jurisdictions are often called "capitals", but this is typically the case only in countries with some degree of federalism, where major substate jurisdictions have an element of sovereignty. In unitary states, "administrative center" or other similar terms are typically used. For example, the seat of government in a state of the United States of America is usually called its "capital", but the main city in a region of England is usually not. At lower administrative subdivisions, terms such as county town, county seat, or borough seat are usually used.

Historically, the major economic center of a state or region often becomes the focal point of political power, and becomes a capital through conquest or amalgamation. This was the case for London and Moscow. The capital naturally attracts the politically motivated and those whose skills are needed for efficient administration of government such as lawyers, journalists, and public policy researchers. A capital that is the prime economic, cultural, or intellectual center is sometimes referred to as a primate city. Such is certainly the case with London and Buenos Aires among national capitals, and Irkutsk or Salt Lake City in their respective state or province.

Capitals are sometimes sited to discourage further growth in an existing major city. Brasília was situated in Brazil's interior because the old capital, Rio de Janeiro, and southeastern Brazil in general, were considered over-crowded.

The convergence of political and economic or cultural power is by no means universal. Traditional capitals may be economically eclipsed by provincial rivals, as occurred with Nanjing by Shanghai. The decline of a dynasty or culture could also mean the extinction of its capital city, as occurred with Babylon and Cahokia. Many present-day capital cities, such as Abuja, Brasília, Canberra, Islamabad, Ottawa and Washington, D.C. are planned cities, purposefully located away from established population centres for various reasons, and have become gradually established as new business or commercial centres.