Nine formulations of nonrelativistic quantum mechanics are reviewed. These are the
wavefunction, matrix, path integral, phase space, density matrix, second quantization,
variational, pilot wave, and Hamilton–Jacobi formulations. Also mentioned are the many-
worlds and transactional interpretations. The various formulations differ dramatically in
mathematical and conceptual overview, yet each one makes identical predictions for all
experimental results.© 2002 American