Question

similarities and differences between ancient Greece and at present

Answer 1

Ancient Greece was a bunch of city states and a few small kingdoms. Today’s Greece is a unitary state. Geographically, Greece is still where it was in Antiquity, except for the coast of Asia Minor (definitely lost in 1923). The political power center is still in the South (the huge Athens agglomeration), just like Athens was the main political player in Antiquity. The second power center (political, economical) remains the same: Thessaloniki, Macedonia, second in most of ancient times, as well as nowadays. The islands have lost much of their inhabitants (Crete is a probable exception). They had a much higher economical and political weight in Antiquity.
Greek language: now with a unified, standard grammar (and an easy one), easy pronunciation too. These are the main differences with the Ancient Greek dialects.
Ancient Greeks were polytheists. Today’s Greeks are Orthodox, possibly more out of a long Byzantine tradition than by conviction. They are still very fond of their mythology.
Genetically ? Let’s not be racists. Over the centuries, Greece has “absorbed” quite a number of Albanians (Ancient Illyrians). Some Slavs too. Very few or no Turks at all (they all left in 1923–24). The Muslims of Thrace, a little more than 1% of the total Greek citizens, were allowed to stay.
As in the past, Greeks are passionately divided over politics. Still more passionately over… soccer !

Answer 2

Becoming Ancient Greek

Although ancient and modern forms of the Greek language share many traits, it would be misleading to consider the two varieties of Greek identical. In fact, the concept of "Ancient Greek” is misleading. For centuries, Greek was split into more than seven regional dialects. Only in the fourth century B.C., under Alexander the Great, did a shared language develop. It was known as ''Koiné'' or ''Common Greek.'' It was from Koiné that ancient Greek, as it is understood today, was born

Making Modern Greek

Modern Greek has shed many of the grammatical rules of its ancient predecessor. For instance, ancient Greek had a certain verbal mood known as the “optative,” which was used when expressing a wish or desire. Modern Greek has dispensed with that nuance-- as it has the “dual,” which was reserved for occasions used when a speaker wanted to describe two of something. And these grammatical changes, along with other shifts such as the elimination of certain prefixes and the adoption of the gerund (also known as the "-ing" verb form) are just a few of the relatively minor changes that distinguish ancient Greek from its modern counterpart.