It took more than 200 years for the Greek people to choose an official language — it wasn't as easy as you would think!
The Greek people grappled with a strange, but not all too unusual problem from 1766 until 1976. They had to decide what the official language of Greece would be and they had to choose one of two options. It was a highly controversial topic in the 19th and 20th centuries.
The dispute was about whether the language of the Greek people (Demotic Greek) or a cultivated imitation of Ancient Greek (katharevousa) should be the official language. The language phenomenon in question—which also occurs elsewhere in the world—is called 'diglossia.'
Diglossia refers to the coexistence of two—in extreme cases—completely different forms of a language that greatly exceed the usual stylistic difference between written and spoken word. Usually there is a 'higher' more formal language co-existing with a 'lower' form of the language that is spoken in homes, market places and among friends. One can therefore say there is a formal and informal version of the same language.
In Greece 'katharevousa' (ancient Greek) was the formal, high version of the language and demotic Greek was the common or 'lower' version of the language. The dispute was finally settled in 1976 when demotic Greek was chosen as the official language of Greece.