The term "civilization," as used by social scientists and historians, refers to a sophisticated society distinguished by the existence of cities.
Now, since they're not as obvious, it's also necessary to talk about what those things actually signify. Specialization and hierarchy are aspects of social complexity. In early tribal and hunter-gatherer communities, the majority of individuals would do largely the same tasks. Almost everyone would engage in some hunting, tend to their own gardens to provide food, craft their own tools, and other activities. People who were skilled at a specific activity may cooperate and share more often. However, a hunter-gatherer group would not, for instance, have members who only caught tiny animals, dug up roots, and so on. When society advances, artisan and professional experts become full-time occupations. People exist who only practice prayer, manufacture pottery, or engage in other religious rites, for example. You also receive hierarchy of rank that is clearly stated. Instead of true monarchs, which arise with civilization, leadership positions in primitive communities typically belong to first among equals or persons with restricted discretion or responsibility for forging agreement.
Cities are substantial, long-term settlements. A population of around 5000 individuals is considered to be "big" as a general rule. It is just not practicable for everyone, much alone the majority of the people, to make a living from farming. A significant proportion of professional and craft experts who are sustained by commercial exchange rather than subsistence labour must exist in communities that size. Additionally, they frequently feature imposing structures like city walls or temples.
Thanks,
Eddie