America, South Asia and Australasia use the term “sister cities” or “twin cities.” In China, it is the term “Yuh`o chengshe”, friendly cities.  Sometimes other government agencies include a partnership relationship, such as the agreement between Hainan provinces in China and Jeju-do in South Korea. The twelve is a twinning of cities with a city from each of the Member States of the European Union.   Although not legally binding, signing a formal partnership “sworn” or agreement facilitates the establishment of a long-term relationship of trust. Its form and content are not defined and can be modified according to the type of partnership established and the will of the twin cities. The twinning of cities is not a new concept for human society. For years, there have been partnerships that date back to Europe in the second century. These links were limited to cities and municipalities (local authorities) in the early years. Since then, links have been established between schools, churches, libraries, port authorities, airports, radio and television stations, postal services and other local authorities, and charities, regional, regional and provincial governments. Twinning agreements are legal or social agreements between two cities to promote trade and tourism. Institutions, organizations and governments at the second and third levels are committed to participating in joint exchanges and activities to enrich partners. The goal is to find strength in their unity. For a long time, twinning was considered a sterile activity.
This idea is now considered superfluous, given that, since the Second World War, partnership agreements for the promotion of peace and cultural exchanges have multiplied and some worthy successes have been achieved. According to a McKinsey study, one-third of the world`s GDP will come from only 100 cities. At the heart of this change is globalization, which strengthens trade flows between regions and shifts economic power to the emerging economies of China and India or the cities of those regions. “It`s cities, not nations, that fuel the global economy and drive growth through productivity, innovation and job creation,” says David Adam, founder of Global Cities, which advises cities on positioning, branding and investment opportunities.