The concept of the -dependent average dwell time ( DADT) is presented for both continuous-time and discrete-time switched systems. Some new stability criteria for switched systems are obtained under the DADT approach, which depends on the choice of the classification function . The relationships among the classic ADT approach, the mode-dependent ADT approach and the proposed one are also discussed, which shows that those existing approaches can be unified to the new one. More concretely, stability results based on ADT/MDADT schemes can be regarded as some special cases of our results with specific functions . The obtained switching design by the new approach is more flexible and practical. At last, a numerical example with some comparisons among the differences in the selection of is included to explain the validity and advantages of the new technique.INDEX TERMS Switched systems, stability, stable subsystems, -dependent average dwell time.