The definition of symbiosis has varied among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (i.e. mutualistic, commensalistic, or parasitic).
The Golden Pledge, which is a System Plus Warranty with a 20 year leak guarantee, can pay for itself within the first ten years, sometimes many times over. The System Plus transforms the normal warranty by removing the small print.
pledge (plural pledges) A solemn promise to do something. Something given by a person who is borrowing money etc to the person he has borrowed it from, to be kept until the money etc is returned. A person who has taken a pledge of allegiance to a college fraternity, but is not yet formally approved.