While the concept of complementarity can be discussed via two experimental extremes, continuous tradeoff is also possible. The wave-particle relation, introduced by Daniel Greenberger and Allaine Yasin in 1988, and since then refined by others, quantifies the trade-off between measuring particle path distinguishability, D , and wave interference fringe visibility, V : D 2 + V 2 ≤ ≤ 1 The values of D and V can vary between 0 and 1 individually, but any experiment that combines particle and wave detection will limit one or the other, or both. The detailed definition of the two terms vary among applications, but the relation expresses the verified constraint that efforts to detect particle paths will result in less visible wave interference.