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.
1 Pre-engagement ring, a ring worn to signify a commitment to a monogamous relationship (a promise to commit to the relationship). 2  Purity ring, a ring worn to signify a pledge to sexual abstinence until married.  3 Promise Ring (song) , a 2007 song by American entertainer Tiffany Evans.