Median
Named by 2 essays across 2 fields — each of them below, with the objects they name alongside it.
The median of many small averages
Knowing only that a quantity has a finite spread, the plain average of n samples can be promised to within σ/√(nδ) with confidence 1 − δ, and no better — Chebyshev's bound is tight, and rare large jumps achieve it. Cut the same samples into a dozen blocks, average each block, and take the median of the averages, and the promise improves to within about σ√(log(1/δ)/n). Nothing about the data has been assumed beyond the spread; only the way of combining it has changed.
The matching in the middle
List every stable matching of a market, give each member their stable partners sorted from best to worst, and hand each the one in the middle. Nothing says the result should even be a matching — two people might pick the same partner — and yet it always is one, it is always stable, and the other side gets its median partners too.
Named alongside it
The objects these essays reach for when they reach for this one.
Blocking pairChebyshev inequalityConfidenceEstimatorExhaustive searchFairnessHeavy tailsHoeffding inequalityLatticeMedian of meansPolytopePreference profile