Nonperturbative QCD contributions to the inclusive semileptonic decay of theB meson consist of the dynamic and kinematic components. We calculate the decaywidth in an approach based on the light-cone expansion and the heavy quarkeffective theory, which is able to include both components of nonperturbativeQCD contributions. The kinematic component results in the phase-space extensionand is shown to be quantitatively crucial, which could increase the decay widthsignificantly. We find that the semileptonic decay width is enhanced bylong-distance strong interactions by +(9\pm 6)%. This analysis is used todetermine the CKM matrix element |V_{cb}| with a controlled theoretical error.Implications of the phase-space effects for the nonleptonic decay widths of bhadrons are briefly discussed. The experimental evidence for the phase-spaceeffects is pointed out.
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