An exclave is a portion of a state or territory geographically separated from the main part by surrounding alien territory (of one or more states). Many exclaves are also enclaves. Enclave is sometimes used improperly to denote a territory that is only partly surrounded by another state. Vatican City and San Marino, enclaved by Italy, and Lesotho, enclaved by South Africa, are the only completely enclaved states. Unlike an enclave, an exclave can be surrounded by several states. The Azeri exclave of Nakhchivan is an example of an exclave.
Semi-enclaves and semi-exclaves are areas that, except for possessing an unsurrounded sea border (a coastline contiguous with international waters), would otherwise be enclaves or exclaves.:116:12–14 Enclaves and semi-enclaves can exist as independent states (Monaco, Gambia and Brunei are semi-enclaves), while exclaves always constitute just a part of a sovereign state (like the Kaliningrad Oblast).
A pene-enclave is a part of the territory of one country that can be conveniently approached – in particular by wheeled traffic – only through the territory of another country.:283 Pene-enclaves are also called functional enclaves or practical enclaves.:31 Many pene-exclaves partially border their own territorial waters (i.e., they are not surrounded by other nations' territorial waters), such as Point Roberts, Washington. A pene-enclave can also exist entirely on land, such as when intervening mountains render a territory inaccessible from other parts of a country except through alien territory. A commonly cited example is the Kleinwalsertal, a valley part of Vorarlberg, Austria, that is only accessible from Germany to the north.
The word enclave is French and first appeared in the mid-15th century as a derivative of the verb enclaver (1283), from the colloquial Latin inclavare (to close with a key). Originally, it was a term of property law that denoted the situation of a land or parcel of land surrounded by land owned by a different owner, and that could not be reached for its exploitation in a practical and sufficient manner without crossing the surrounding land. In law, this created a servitude of passage for the benefit of the owner of the surrounded land. The first diplomatic document to contain the word enclave was the Treaty of Madrid, signed in 1526.:61
Later, the term enclave began to be used also to refer to parcels of countries, counties, fiefs, communes, towns, parishes, etc. that were surrounded by alien territory. This French word eventually entered the English and other languages to denote the same concept although local terms have continued to be used. In India, the word "pocket" is often used as a synonym for enclave (such as "the pockets of Puducherry district"). In British administrative history, subnational enclaves were usually called detachments or detached parts, and national enclaves as detached districts or detached dominions. In English ecclesiastic history, subnational enclaves were known as peculiars (see also Royal Peculiar).