Thus, the lifetime of a particle is the direct inverse of the particle's resonance width. For example, the charged pion has the second-longest lifetime of any meson, at 2.6033 × 10 s. Therefore, its resonance width is very small, about 2.528 × 10 eV or about 6.11 MHz. Pions are generally not considered as "resonances". The charged rho meson has a very short lifetime, about 4.41 × 10 s. Correspondingly, its resonance width is very large, at 149.1 MeV or about 36 ZHz. This amounts to nearly one-fifth of the particle's rest mass.