The weak nuclear force or weak interaction is one of the four fundamental forces of nature. It is most commonly thought to be the cause of beta decay and the associated radioactivity. It is carried by the W bosons (W+ and W-) and Z bosons (Z0).
The weak interaction affects:energy, mass and charge - effectively change into each other.
With a field strength some 109 times less than the strong nuclear force (10-18 m), its influence is limited to action within the atomic nucleus. This short range is explained by the large mass of the weak exchange particles (about 90 GeV).
See also SU(3)XSU(2)XU(1).