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. n. 1. A solemn binding promise to do, give, or refrain from doing something: signed a pledge never to reveal the secret; a pledge of money to a charity. 2. a. Something given or held as security to guarantee payment of a debt or fulfillment of an obligation.