Using a round trip ticket one way only

Unless you purchase a Full fare ticket most round trips are discounted highly restricted tickets, so if you use only the outbound portion with no intention of using the return then no problem, however if you purchased the ticket only to use the return portion then you are in for a surprise, because if you did not fly the outbound then the return is automatically canceled and the Airline will not honor that ticket. This is because sometimes buying a round trip ticket is cheaper than a one way and the passenger shopping around will see the return segment of a round trip and the portion that they really intend to use is a lot less expensive than buying that segment separately.