In the United Kingdom, the term « twin cities » is the most widely used; the term « sister cities » is generally used for agreements with cities in North and South America.   On the European continent, the most commonly used terms are `twin cities`, `twin cities`, `twin cities` and `friendship cities`. The European Commission uses the term `twin cities` and refers to the process as `twinning cities`.   Spain uses the term « ciudades hermanadas, » which means « sister cities. » Germany, Poland and the Czech Republic use the partner city (De) / miasto partnerskie (Pl) / partnerské mesto (Cz), which means « partner city » or « partner city ». France uses twin city (twinning, twinning city or city) and Italy a gemellaggio (partnership) and comune gemellato (common partner).  In the Netherlands, the terms « Partnerstad » or « Stedenband » (« urban borrowing » when it comes to mutual assistance). In Greece, the word « Adelfopiisi – Fraternity » was adopted. In Iceland, the terms vinab`ir (friends cities) and Vinaborgir (friends cities) are used. In the former Soviet bloc, « twin cities » and « twin cities » were used, with the « Ru » (sworn brother cities).   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.
It is therefore important for leaders to understand how global economic factors can influence the competitiveness of their city/region and to determine how their unique assets can cope with the effects of globalization, so that they can benefit from new trade flows, direct investment, job creation and innovation, and remain an attractive offer in a global economy.