French philosopher Henri Bergson first made the distinction.

Synchrony and diachrony are two different and complementary viewpoints in linguistic analysis:

  • a diachronic approach considers the development and evolution of a language [or text] through history.
  • a synchronic approach considers a language [or text] without taking its history into account.

— Wikipedia

How does this relate to short fiction? Short fiction scholar Mary Rohrberger has argued that novels are typically diachronic whereas short stories are typically synchronic.

What do you think?