Inclusive decay $B\to \eta X$

Using data samples taken at the $\Upsilon \mathrm{}\left(4S\right)\mathrm{}$ resonance and nearby continuum $e^{+}{e}^{-}$ annihilation with the CLEO-II detector at CESR, we have measured the inclusive branching fraction $\mathcal{B}(B\to \eta X)=(17.6\mathrm{}\pm 1.1\pm 1.2)\%$, and the momentum distribution of the $\eta$ mesons from $B$ meson decay. The $\eta$ yield cannot be explained as arising solely from the decay of intermediate charmed mesons.