Since it is clear that | ψ ψ ⟩ ⟩ alone does not define a modality, what is its status ? If N ≥ ≥ 3 , one sees easily that | ψ ψ ⟩ ⟩ is associated with an equivalence class of modalities, belonging to different contexts, but connected between themselves with certainty, even if the different CSCO observables do not commute. This equivalence class is called an extravalence class, and the associated transfer of certainty between contexts is called extracontextuality. As a simple example, the usual singlet state for two spins 1/2 can be found in the (non commuting) CSCOs associated with the measurement of the total spin (with S = 0 , m = 0 ), or with a Bell measurement, and actually it appears in infinitely many different CSCOs - but obviously not in all possible ones.