The decreasing order of nucleophilicity

I) ${\mathrm{CH}}_3\mathrm{C}{\mathrm{H}}_2\overline{\mathrm{O}}$

II) $\mathrm{C}{\mathrm{H}}_3\overline{\mathrm{O}}$

III) $\overline{\mathrm{O}}\mathrm{H}$

IV) ${\mathrm{CH}}_3\stackrel{⊝}{\mathrm{S}}$

More the electron density on the anion better nucleophilicity & more EN element can hold the $e^{-}s$ is strongly as such nucleophilicity will be less.