Depending on who replies, the answer to your question, as it pertains specifically to the ancient Greek civilization, might include: their philosophers, their classical theater, their architecture, or their literature (most significantly, the epics of Homer). However, I think most people, if faced with the choice of picking a single contribution, would say the advances in systems of governance leading toward representative democracy.
Architecture
-The Greek Parthenon influenced many buildings after it's time.
Like the US Supreme Court building and the White House.
Literature
-The first great epic poems by Homer (The Iliad and The Odyssey) that later were used as basic texts for the education of generations of Greek men.
Military Systems
-The military system of the Hoplites, heavily armed infantry soldiers/foot soldiers that marched in rectangular formation, were used later on with Roman soldiers, the Revolutionary War, etc.
Government
-The end of tyranny in Greek city-states led to the development of democracy and oligarchy.
Entertainment
-Drama was created by the Greeks. The first of the Greek drama plays were tragedies. We still have tragedies today.
(these are all facts because I got them from my world history textbook)
they gave us many things such as
The list could literally go on forever, however, in my opinion, government and scientific discoveries are the most important.
the hierarchical classification scheme
Airbus is a pan-European consortium, with significant contributions from France, Germany, Spain and the UK.
The last two lines of "Ode on a Grecian Urn" by John Keats are: "Beauty is truth, truth beauty,βthat is all / Ye know on earth, and all ye need to know."
The most significant feast day is Pentecost as it is the birthday of the Church. It is followed by Easter and Christmas.
The theory of evolution by natural selection. Sexual selection. Just to name the two most important contributions of Charles Darwin.
I can give you several sentences.The most significant thing about this problem is that it's going to be hard to get everyone working together.Color is the most significant difference between those two birds.The most significant trait for a human is the ability to think.
the 2 contributions of is...
The Maya made significant advancements in mathematics, developing a sophisticated numbering system and understanding of concepts like zero. They also made important contributions in astronomy, creating accurate calendars and observing celestial events with precision.
Albert Einstein is known for his contributions to theoretical physics, most notably the theory of relativity which encompasses both the special theory of relativity and the general theory of relativity. While he proposed other theories and made significant contributions to quantum mechanics, it is the theory of relativity that he is most famous for.
Two Roman contributions to architecture are the dome and the Tuscan order of column.
Diffraction is most significant when light is passing through very small gaps like two blocks very close together.
The roots of the war started between two Grecian cities, Epidamnus and Corinth, in 436 BC.