When two countries or political divisions share a common border, they are said to be contiguous, adjoining, or adjacent to one another. This means their borders physically touch, without any separation by water or other countries between them. There are several related terms to describe the specific relationship between contiguous political entities.
Adjacency and Contiguity
The most common terms used are “adjacent” and “contiguous,” which are synonyms when referring to borders. Both words mean sharing a common boundary or border without anything interrupting the connection. For example, the United States and Canada are adjacent because their land borders touch. Mexico and Guatemala are contiguous because they border each other without any other country separating them.
Adjacency and contiguity describe the lack of interruption along a shared border. This is different from proximity or nearness in location. Two countries can be proximate or near each other without actually touching borders. However, contiguous or adjacent nations will always share an uninterrupted boundary line.
Land and Maritime Borders
The adjacency between countries most commonly refers to land borders. Canada and the U.S. have an entirely land-based border, marked along the 49th parallel from the Atlantic to the Pacific Ocean. However, adjacency can also occur across maritime borders. Maritime borders are boundaries drawn across bodies of water, defining the territorial waters claimed by each country.
For example, Russia and Japan share a maritime border despite being separated by water. Their Exclusive Economic Zones in the Sea of Okhotsk are adjacent at a median line between the two countries. They have negotiated agreements on fishing rights and resource extraction in these adjoining maritime border areas.
Enclaves and Exclaves
In some cases, the borders between adjacent countries can create areas of disjointed territory. These take the form of enclaves and exclaves.
- An enclave is an area of one country that is entirely surrounded by the territory of another country.
- An exclave is an area of one country that is detached or separated from the main part of the country by another country.
For example, the Republic of San Marino is an enclave fully contained within Italy. The border between Italy and San Marino marks the boundary line around the enclave. Ceuta is a Spanish exclave on the north coast of Africa, sharing a border with Morocco.
Shared Borders and International Relations
The interactions between contiguous countries have an enormous impact on international relations. Adjacent nations must cooperate on border security, transport links, trade policies, and management of shared resources. Tensions can arise from territorial disputes over exact boundary lines or concerns about infiltration and crime across borders.
On the other hand, proximity also facilitates cultural exchange and economic collaboration. Joint infrastructure investments like roads, railways, pipelines and electricity networks can foster interdependence. Trade thrives due to ease of transportation across open borders. Tourists and workers can freely move between adjoining countries to experience new cultures.
Diplomatic relations must be maintained through ongoing dialogue between governments of contiguous states. The policies of one inevitably affect the other across their shared border. This interconnection requires bilateral or regional cooperation between neighboring countries on issues ranging from security to immigration to environment.
Notable Examples of Contiguous Countries
Some of the most extensive contiguous land borders in the world include:
- United States and Canada: 5,525 miles
- Russia and Kazakhstan: 4,254 miles
- Argentina and Chile: 2,693 miles
- China and Mongolia: 2,646 miles
The countries with the most contiguous neighbors include:
- Germany: 9 neighbors
- Russia: 14 neighbors
- China: 14 neighbors
- Brazil: 10 neighbors
Some examples of enclaves and exclaves created by national borders:
- Kaliningrad, Russia (exclave between Poland and Lithuania)
- Nakhchivan, Azerbaijan (exclave bordering Armenia, Iran, Turkey)
- Baarle-Hertog, Belgium (enclaves within the Netherlands)
- Madha, Oman (enclave within the United Arab Emirates)
Use of Bordering, Vicinity, Proximity
“Bordering” is a synonym for adjacent, but less commonly used. For example, “Germany borders 9 other countries.”
“Vicinity” and “proximity” imply being near or neighboring without directly abutting. “France and the UK are in close vicinity across the English Channel.” “The proximity of the U.S. and Russia across the Bering Strait has strategic importance.”
Shared Boundaries at Other Scales
Contiguity and adjacency also describe the shared borders between sub-national political and geographic entities. For example:
- States in the United States
- Provinces and territories of Canada
- Counties within a state
- Cities that directly abut each other in an urban area
At local levels, municipal and county governments must coordinate across their shared boundaries just as national governments do. Issues like transportation infrastructure, economic development, watershed management, and emergency services require planning and cooperation across adjacent jurisdictions.
Non-Political Adjacency
Outside of political geography, the term adjacent can describe any bordering or contiguous relationship. In anatomy, adjacent organs or structures are next to each other. In mathematics, adjacent angles share a common vertex point. In geography more broadly, ecological regions, climate zones, or landform features can be described as adjacent if they share an uninterrupted boundary.
Conclusion
Contiguity and adjacency are vital concepts in geography and political relationships. Nations must engage diplomatically and economically with their contiguous neighbors because of their shared borders. While borders can be a source of conflict, they can also provide opportunities for trade, cultural exchange, and regional integration when countries build constructive ties across boundaries.
| Term | Definition |
|---|---|
| Contiguous | Sharing a common border; adjoining, abutting |
| Adjacent | Next to each other; adjoining or abutting |
| Enclave | Territory fully surrounded by another country |
| Exclave | Territory detached or separated from main part of country |
