Why do we call a civilization a civilization?

There are two ways in which we use the word 'civilisation' to refer to society. 

The first simply refers to a particular society at a particular point in time. For example the Ancient Egyptian civilisation, future civilisations, or early Mayan civilisation. Here we don't refer to the "level" of civilisation within that society, rather just that the society existed. 

The second way in which we use the word is for when a society achievescivilisation....

There are two ways in which we use the word 'civilisation' to refer to society. 

The first simply refers to a particular society at a particular point in time. For example the Ancient Egyptian civilisation, future civilisations, or early Mayan civilisation. Here we don't refer to the "level" of civilisation within that society, rather just that the society existed. 

The second way in which we use the word is for when a society achieves civilisation. That is, when a large society has reached an advanced state of organisation and has a distinct cultural identity.

The word comes from the Latin, "civis", meaning citizen. To have citizens, there must be a government. This sets a requirement for organisational and economic structure.

Here are a set of text-book definitions:

Civilization is a form of human culture in which many people live in urban centers, have mastered the art of smelting metals, and have developed a method of writing.

The first civilizations began in cities, which were larger, more populated, and more complex in their political, economic and social structure than Neolithic villages.

One definition of civilization requires that a civilized people have a sense of history -- meaning that the past counts in the present.

Overall, it is much easier to describe what a civilisation entails, rather than define it. What for example, is the definition of an 'advanced' society. 

Of course you can use the word more widely. For example, describing a person as civilised means they are polite and have manners - advanced socially.

Or, if you are lost in the woods, you would be seeking any form of civilisation. Here that could mean a basic hut, or just another human, or a way to point you to safety.