ITU‐T's Technical Reports and Specifications 761 3 Definitions 3.1 Terms defined elsewhere 3.1.1 smart sustainable cities: A smart sustainable city is an innovative city that uses information and communication technologies (ICTs) and other means to improve quality of life, efficiency of urban operation and services, and competitiveness, while ensuring that it meets the needs of present and future generations with respect to economic, social, environmental as well as cultural aspects. 3.2 Terms defined in these Technical Specifications These Technical Specifications define the following terms: 3.2.1 City: An urban geographical area with one (or several) local government and planning authorities. 3.2.2 City sustainability: The sustainability of a smart city is based on four main aspects: Economic: The ability to generate income and employment for the livelihood of the inhabitants. Social: The ability to ensure that the well‐being (safety, health, education) of the citizens can be equally delivered despite differences in class, race or gender. Environmental: The ability to protect future quality and reproducibility of natural resources. Governance: The ability to maintain social conditions of stability, democracy, participation, and justice. 4 Abbreviations and acronyms These Technical Specifications use the following abbreviations and acronyms: GHG Greenhouse Gas ICT Information and Communication Technology IDI ICT Development Index ISO International Organization for Standardization KPI Key Performance Indicator OSI Open Systems Interconnection PM10 Particulate Matter up to 10 micrometres in size SSC Smart Sustainable Cities ToR Terms of Reference UN‐Habitat United Nations Human Settlements Programme