Cables are common components in engineering structures.The responses especially nonlinear responses of the cables are complex and need to be analyzed and characterized for dynamic studies of the structures.This research studies the nonlinear behavior of an elastic cable subjected to gravity and a harmonic external excitation exerted at an end of the cable.Both the in-plane and out-of-plane vibrations of the cable are analyzed with utilization of the Periodicity-Ratio(P-R)method.The influences of different system parameters on the nonlinear vibrations of the cable are examined.Periodic,quasiperiodic and chaotic vibrations are all identified.Significantly,the nonlinear responses neither periodic or quasiperiodic nor chaotic are found in the research.Theoretically,P-R method is capable of characterizing infinite types of responses of the cable in between period and chaotic responses.A periodic-quasiperiodic-chaotic region diagram is developed for graphically characterize the nonlinear behavior of the cable,with employment of the P-R method.