Fall

As i rode my bike home today along the bike path, i noticed that fall seems to have struck the Ahr Valley with a vengence. Then i got to thinking- if Spring has sprung, can one say that Fall has fallen? I mean, i suppose it's grammatically ok, but it sounds a bit off. i started thinking maybe it was just a matter of finding a synonym for fallen. Here is what Thesaurus.com pulled up:

1 thesaurus results for: fallen
Main Entry: fallen
Part of Speech: adjective
Synonyms: dead, debased, degraded, deposed, depreciated, disgraced, dropped, immoral, lost, prostrate, shamed, sinful, slain

I think i may have maybe not done this search using the right word. Because, as sure as i am that no one really says "Fall has fallen", i am even more sure that no one would ever say "Fall has depreciated" or "Fall has dropped". Maybe i should hit the drawing board again here. There seems to be some fundamental flaws in my thought process on this one...