In its most basic definition, civilization refers to a human society that is organized enough so that its citizens can live comfortably, and can think about things like art and education. Civilization has its roots in the ancient world, with some of the earliest examples emerging from the Nile valley of Egypt, around the Indus river region of Pakistan, and in the Huang He valley of China. These people developed cities, created writing systems, and domesticated animals. They also specialized in different jobs, with some people becoming farmers and others becoming potters, weavers, or priests. They worked together to build complex buildings, and they created governments with a hierarchy of classes: king, nobles, freemen, peasants, and slaves.
The concept of civilization has expanded over time, and today it encompasses a much wider range of activities. It can be seen in agrarian societies that still work hard to produce food, but have evolved into modern economies that value higher-level education and artistic production. It can also be found in some parts of the world, where populations have made a conscious choice to embrace certain principles of a westernized culture, even if those practices run counter to their traditional beliefs and values.
Civilization requires a large population living in the same area, sharing a common language and cultural traits. These groups are often referred to as a nation, though there may be more than one such group within a larger territory. The term can also be applied to a broader region, such as an entire continent or the globe. Some experts argue that a global civilization is now in progress, although it will take centuries for it to mature.
For a civilization to develop, it must have certain key features, most importantly an adequate supply of food. The transition from hunter-gatherer to farmer life was a milestone in human history, making it possible for humans to live in cities and focus on other aspects of life, including art, learning, and religion.
As the human race became more sedentary, it was important to find ways to store surplus food in order to avoid starvation in case of disaster or war. This led to the development of farming and other types of agricultural techniques, along with a system of trade that enabled the spread of new ideas and technologies.
As these developments continued to evolve, the social structures of human communities grew more complex and rigid. The first kings emerged, and people who controlled food surpluses were able to create jobs in the form of officials (such as those who collected taxes) and engineers (who planned irrigation systems). As the development of agriculture allowed for higher levels of specialization in labor, other roles arose that required education and training, such as priests. These positions, plus a growing number of wealthy landowners, eventually created highly stratified social hierarchies with five to seven inherited social classes: king, nobles, freemen, servants, and slaves.