# Why are nucleophiles Lewis bases?

Well, what is a $\text{Lewis Base}$?
And by definition a $\text{Lewis Base}$ is an electron-pair donor. Now the electron pair is conceived to be donated to an electrophile in a nucleophilic substitution reaction...and this is precisely what occurs in such a reaction....
${\underbrace{H {O}^{-} + {H}^{+}}}_{\text{Lewis base + Lewis acid}} r i g h t \le f t h a r p \infty n s {H}_{2} O \left(l\right)$