A province is a territorial unit, almost always a country subdivision.

Roman provinces
In many countries, a province is a relatively small non-constituent level of sub-national government (similar to a county in many English-speaking countries). In others it is an autonomous level of government and constituent part of a federation or confederation, often with a large area (similar to a US state). In France and China, province is a sub-national region within a unitary state. This mean the province can be abolished or created by the central government.
For instance, a province is a local unit of government in Belgium, Spain and Italy, and a large constituent autonomous area in Canada, Congo and Argentina. In Italy and Chile a province is an administrative sub-division of a region, which is the first order administrative sub-division of the state. Italian provinces consist of several administrative sub-divisions called comune (communes). In Chile they are referred to as comunas
The "Province of Northern Ireland" is the only British territory called "province" today. In this case, the title province suggests separateness along the lines of Canadian usage. The title "province" above all reflects Northern Ireland's unique autonomy within the UK immediately after its foundation in 1921, but today Northern Ireland varies between a devolved government and direct rule. Northern Ireland is effectively a constituent nation of the United Kingdom.
Various overseas parts of the British Empire had the colonial title of Province (in a more Roman sense), such as the Province of Canada and the Province of South Australia (the latter to distinguish it from the penal 'colonies' elsewhere in Australia). Equally, for instance, Mozambique was a "province" as a Portuguese colony.

Provinces in modern countries
In France, the expression en province still tends to mean "outside of the region of Paris". (The same expression is used in Peru, where en provincias means "outside of the city of Lima" and in Romania, where în provincie means "outside the region of Bucharest".) Prior to the French Revolution, France consisted of various governments (such as Ile-de-France, built around the early Capetian royal demesne) some of which were considered as provinces, although the term would be used colloquially to describes lands as small as a manor (châtellenie). Mostly, the Grands Gouvernements, generally former medieval feudal principalities (or agglomerates of such), were the most commonly referred to as provinces. Today, the expression is sometimes replaced with en région, as that term is now officially used for the secondary level of government.
In historical terms, Fernand Braudel has depicted the European provinces—built up of numerous small regions called by the French pays or by the Swiss cantons, each with a local cultural identity and focused upon a market town—as the political unit of optimum size in pre-industrial Early Modern Europe and asks, "was the province not its inhabitants' true 'fatherland'?" (The Perspective of the World 1984, p. 284) Even centrally organized France, an early nation-state, could collapse into autonomous provincial worlds under pressure, such as the sustained crisis of the Wars of Religion, 1562—1598.
For 19th and 20th-century historians, "centralized government" had been taken as a symptom of modernity and political maturity in the rise of Europe. Then, in the late 20th century, as a European Union drew the nation-states closer together, centripetal forces seemed to be moving towards a more flexible system composed of more localized, provincial governing entities under the European umbrella. Spain after Franco is a State of Autonomies, formally unitary, but in fact functioning as a federation of Autonomous Communities, each one with different powers. (see Politics of Spain). While Serbia, the rump of the former Yugoslavia, fought the separatists in the province of Kosovo, at the same time the UK, under the political principle of "devolution" established local parliaments in Scotland, Wales and Northern Ireland (1998). Strong local nationalisms surfaced or developed in Cornwall, Languedoc, Catalonia, Lombardy, Corsica and Flanders, and east of Europe in Abkhasia, Chechnya and Kurdistan.

Geology
In many federations and confederations, the province or state is not clearly subordinate to the national or "central" government. Rather, it is considered to be sovereign in regard to its particular set of constitutional functions. The central and provincial governmental functions, or areas of jurisdiction, are identified in a constitution. Those that are not specifically identified in the constitution are called "residual powers". These residual powers lie at the provincial (or state) level in a decentralised federal system (such as the United States and Australia) whereas in a centralised federal system they are retained at the federal level (as in Canada). Nevertheless, some of the enumerated powers can also be very significant. For example, Canadian provinces are sovereign in regard to such important matters as property, civil rights, education, social welfare and medical services.
The evolution of federations has created an inevitable tug-of-war between concepts of federal supremacy versus "states' rights". The historic division of responsibility in federal constitutions is inevitably subject to multiple overlaps. For example, when central governments, responsible for "foreign affairs", enter into international agreements in areas where the state or province is sovereign, such as the environment or health standards, agreements made at the national level can create jurisdictional overlap and conflicting laws. This overlap creates the potential for internal disputes that lead to constitutional amendments and judicial decisions that significantly change the balance of powers.
In unitary states such as France and China, provinces are subordinate to the national or central government. In theory, the central government can abolish or create provinces within its jurisdiction.

Legal aspects
Not all "second-level" political entities are termed provinces. In Arab countries the secondary level of government, called a muhfazah, is usually translated as a governorate. This term is also used for the historic Russian guberniyas, (compare to modern-day oblast). In Poland, the equivalent of province is województwo, often translated as voivodeship.
In Peru, provinces are a tertiary unit of government, as the country is divided into twenty-five regions, which are then subdivided into 194 provinces. Chile follows a similar division being divded into 15 regions, which a then divided into a total of 53 provinces each being run by a governor appointed by the president.
There are also provinces in New Zealand, but the country is not seen as a "federal" country. However, the provinces do have a few duties like collecting rates and each province has its own Health Board and District Prisons Board.
Some provinces are as large and populous as nations. The most populous province is Henan, China, pop. 93,000,000. Also very populous are several other Chinese provinces, as well as Punjab, Pakistan, pop. 85,000,000.
The largest provinces by area are Xinjiang, China (1,600,000 km²) and Quebec, Canada (1,500,000 km²).

Current provinces

Current provinces and polities translated "province"

Historical provinces

Pharaonic Egypt : see nome (Egypt)
Achaemenid Persia (and probably before in Media, again after conquest and further extension by Alexander the Great, and in the larger Hellenistic successor states : see satrapy
Provinces of the Roman Empire
Byzantine Empire : see exarchate, thema
Frankish (Carolingian) 're-founded' Holy Roman Empire : see gau and county
Caliphate and subsequent sultanates : see Emirate
Khanate can also mean a province as well as an independent state, as either can be headed by a Khan
In the Tartar Khanate of Kazan : the five daruğa ('direction')
Mughal Empire : subah
In the Habsburg territories, the traditional provinces are partly expressed in the Länder of 19th-century Austria-Hungary.
The provinces of the Ottoman Empire had various types of governors (generally a pasha), but mostly styled vali, hence the predominant term vilayet, generally subdivided (often in beyliks or sanjaks), sometimes grouped under a governor-general (styled beylerbey). Modern post-feudal and colonial provinces

Governor
Lists of unofficial regions by country
Provincialism
Rise: The Vieneo Province