Reciprocal rank fusion
Merging ranked lists from several retrievers by summing the reciprocal of each result's rank, rather than comparing scores.
By Lattice editorial · Entry last reviewed · method
What it implies
Score-based fusion requires the retrievers to be on a comparable scale, which they are not. RRF sidesteps that entirely by only using positions, which is why it is the default in hybrid search and almost always the right first attempt.