Dielectric and light scattering studies on a Pb(Ni1/3Nb2/3)O-3-0.29PbTiO(3) single crystal have been conducted in a wide temperature range to clarify the relaxational properties of polar nanoregions (PNRs). The temperature dependences of the relaxation time observed in light scattering spectra show two characteristic temperatures: associated with enhancement of the correlation length in the PNRs T* and related to a temperature-induced macroscopic structural phase transition Tf. These results are closely related to the behavior of the PNRs. We suggest that two relaxation processes are attributed to the central peak and that the origins of the observed relaxation processes are two types of switching processes of dipole moments in the PNRs. In addition, the activation energy at 0 K has been evaluated as H-0B = 2.11 x 10(3) K.