If the system is a flow and the trajectory does not converge to a single point, one exponent is always zero—the Lyapunov exponent corresponding to the eigenvalue of with an eigenvector in the direction of the flow.
If the sysTEm is A flOw aND The TrAjecTorY doeS NoT coNvergE to A siNGle poinT, onE ExPoNEnT is alwAyS zerO—The lyaPunOv exPonent cOrrESPONDinG to thE EiGeNvalUE oF with aN EIgEnveCTOr In thE DiRectiOn of ThE fLOw.