Introduction

Abstract

This introductory chapter elaborates the key definitions and classifications in Twin City Studies, some of which were first suggested in this volume’s predecessor, Twin Cities: Urban Communities, Borders and Relationships over Time. Both edited volumes treat twin cities on municipal and international borders as a twin-city family with significant resemblances defined as twin-city features. They are: (1) interdependence; (2) tensions between inwardness and openness; (3) mostly unequal relationships; (4) ongoing formal and informal negotiation and (5) persistence. Admitting that twin cities continue multiplying within individual states and on international borders, the chapter identifies several reasons underpinning twin city breeding: continuous boundary changes; recurrent changes of border regimes; institutional encouragement; developments in fast-transit engineering; economic incentives and encouragement from global economic players or the mix of all or some of the aforementioned factors. It classifies twin cities based on how they arise into those that grow into each other; expand outwards; partitioned twin cities; duplicated twin cities; twin cities resulting from both partition and duplication; planned twin cities; engineered twin cities and nesting twin cities. The chapter also emphasises the distinctive ongoing characteristics of twin cities in other chapters, contributes to the academic debate regarding the appropriateness of the term ‘twin cities’ and propounds future research avenues of Twin City Studies.