(quantum mechanics) The phenomenon in which a wavefunction — initially in a superposition of several different possible eigenstates — appears to reduce to a single one of those states after interaction with an observer: the reduction of the physical possibilities into a single possibility as seen by an observer.

The universal wavefunction or the wavefunction of the universe is the wavefunction or quantum state of the entire universe.

In condensed matter physics, the Laughlin wavefunction pp.