A city is a human settlement of a substantial size. The term "city" has different meanings around the world and in some places the settlement can be very small. Even where the term is limited to larger settlements, there is no universally agreed definition of the lower boundary for their size. In a narrower sense, a city can be defined as a permanent and densely populated place with administratively defined boundaries whose members work primarily on non-agricultural tasks. Cities generally have extensive systems for housing, transportation, sanitation, utilities, land use, production of goods, and communication. Their density facilitates interaction between people, government organizations, and businesses, sometimes benefiting different parties in the process, such as improving the efficiency of goods and service distribution.
The city, one of the world’s biggest phenomenon of the 21st century has evolved greatly over the centuries, particularly in terms of its size, form, structure and composition, while largely maintaining its importance in local and regional development. In just 65 years, the world has experienced a population shift from rural to urban, as witnessed by an increase in the global population living in urban areas from 29.6% in 1950 to 54% in 2015.