Economics is the study of economic mechanisms.

I don't know this system, but the man in charge will explain.

The political systems of Britain and Japan have a great deal in common.

Lately the discount airline ticket system has gotten so complicated that there's a lot about it I can't figure out.

The third is the preservation of environment. In this case, the conservation of energy and resources is needed.

The loss of childhood spontaneity has caused widespread concern, as well as calls for review of the nation's educational and social structures.