The nonet symmetry scheme seems to describe rather well the masses and $\eta -{\eta }^{\prime }$ mixing angle of the ground state pseudoscalar mesons. It is expected that nonet symmetry should also be valid for the matrix elements of the pseudoscalar density operators which play an important role in charmless two-body $B$ decays with $\eta$ or ${\eta }^{\prime }$ in the final state. Starting from the divergences of the $SU(3)$ octet and singlet axial vector currents, we show that nonet symmetry for the pseudoscalar mass term implies nonet symmetry for the pseudoscalar density operators. In this nonet symmetry scheme, we find that the branching ratio $B\to PP$, $PV$ with $\eta$ in the final state agrees well with data, while those with ${\eta }^{\prime }$ are underestimated, but by increasing the $B\to {\eta }^{\prime }$ form factor by 40%–50%, one could explain the tree-dominated $B^{-}\to {\pi }^{-}{\eta }^{\prime }$ and $B^{-}\to {\rho }^{-}{\eta }^{\prime }$ measured branching ratios. With this increased form factor and with only a moderate annihilation contribution, we are able to obtain $62\times {10}^{-6}$ for the penguin-dominated $B^{-}\to K^{-}{\eta }^{\prime }$ branching ratios, quite close to the measured value. This supports the predicted value for the $B\to {\eta }^{\prime }$ form factor in PQCD and light-cone sum rules approach. A possible increase by 15% of $⟨0|\overline{s}i{\gamma }_{5}s|s\overline{s}⟩$ for ${\eta }_0$ would bring the predicted $B^{-}\to K^{-}{\eta }^{\prime }$ branching ratio to $69.375\times {10}^{-6}$, very close to experiment.

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