title_body: A Hypothetical Mediterranean Language Inspired by Both Greek and Latin Here is the scenario:
  
  In or before the Classical Period, a king from some Greek city-state--it doesn't matter which--first brought all the other Greek city-states together to become one unified nation.  Either he or his heir then declared that the whole of the Mediterranean belong to the Greeks.  First phase of the grand plan was to conquer the Mediterranean was to absorb the lands of their closest neighbors, the Roman Republic.  The Republic, weak from the Conflict of the Orders, embraced their Greek conquerors with minimal resistance.  In absorbing Greek and Roman lands together, Greek and Roman culture merged into one, and that includes language.
  
  The inspiration behind this scenario is that both Greek and Roman cultures have such inspirations on modern Western culture that it's hard to decipher where Greek ended and Roman began.  But what if both cultures were merged into one new one?  If you mix Greek with Latin, what should I look out for in regards to grammar?
  
  I ask this because many people are not convinced that Glosa, an auxlang already inspired by both Greek and Latin, won't be the natural answer to this question.
upvoted_answer: The situation you describe, in which Classical Greece invades the Roman Republic, has two probable outcomes. (This is assuming a single language "merged into one" excludes the possibility of both languages coexisting. However, a language can also exert influence on another without supplanting it.)
  
  
  If the Romans adopted (or were forced to adopt) their conquerors' language, which is what happened in other nations after Alexander the Great's conquests later in history, then the spoken language would become Greek. The influence of the Latin language in such a case would exist as a substrate, which could introduce Latin loan words and grammatical structures into Roman Greek.
  If the Romans didn't choose (or weren't forced) to adopt Greek as their language and continued to speak Latin, then Latin would remain the spoken language, but would have Greek influence on vocabulary and grammar, as a superstrate or adstrate. As it is, Latin already has Greek influence on its vocabulary, with learned words like philosophia; but in the case of a Greek conquest, it would probably gain more mundane words as well.
  
  
  A comparable case in history with regard to English could be the Norman invasion of England. Anglo-Norman and English were spoken alongside each other. Eventually, English was the only language spoken of the two in England, but not without considerable influence from Anglo-Norman. Looking at this case might give an idea of how a language could change followed by the invasion of another one.