In Airlines Ticketing and Reservation world What is the difference between : Round Trip & Circle Trip?

A round trip is

any trip that involves one point of departure and one destination, i.e., from point A to point B and back to point A

A circle trip is

any trip that involves more than a single destination, but which returns to the initial point of departure. A simple circle trip, for example, is from point A to point B, point B to point C, and then point C back to point A (and there may be additional points, too, before the return to point A)

Hello, 

The round trip is a trip that involves one point of departure and one destination, i.e., from point A to point B and back to point A.

The Circle Trip is Any trip involving a stopover in addition to the ultimate destination  (e.g. A-->B, B-->C then C-->A using the same or different fare basis codes). 

i create the below Photo to clarify .

Air travel in which the point of origin is also the ultimate destination but is not a round trip because it involves more than one stopovers