Looking for a term, phrase or idiom that best describes a special type of relationship between two parties, not necessarily humans, in which both gain unprecedented benefits. However, such advantages could not be acquired without the relationship; they can continue their own ways without that. In fact, the relationship will add something invaluable.
The desired word should complete such a sentence : There is a —- relationship between concept A and B.
Best Answer
There is a relationship of synergy/ (synergistic relationship) between concept A and concept B working together.
A synergistic relationship is one where two parties, or things, working together, are able to produce a result that is greater than the sum of what they can each do individually.
It is perhaps OED sense 3 of synergy which seems relevant here:
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