Difference between Amphitheater and Amphitheatre

What is the difference between Amphitheater and Amphitheatre?

Amphitheater as a noun is a semi-circular acoustic backdrop behind performers for an outdoor venue. while Amphitheatre as a noun is an open, outdoor theatre, especially one from the classical period of ancient rome.

We hope you now know whether to use Amphitheater or Amphitheatre in your sentence.