Nothing. Nowadays they are all the same.

Technically the word Gyrocopter is a trademark of the Bensen corporation and was used to try and differentiate between the work of Igor Bensen and others.

As a generalisation the CAA tend to use the word Autogyro, manufacturers tend to use the word Gyroplane, personally we like the word Gyrocopter - we think it just sounds better.

What do you think, have some fun and click the poll on the left