A civilization is a group of people who come together through a common culture. Some way to see a culture, is through an own language, a common political organization, a particular sense of art expression and a history that connect this civilization to their ancestors.
Same thoughts, same religion and the same culture are fundamentals to identify a civilization, because those attitudes makes people feel belong and be part of something, and being part of something is one of the basic feelings in our human nature.
To sum up, civilization is a group of people with the same idiom and the same conception of thoughts, manners, and tastes, sharing the same geographical space; having commons rules for being in concord with them as a community. And that is one of the most basic feelings in the 
human nature. Being with others.
