In my text book, it is written that $\ce{NH3}$ is a base. They mentioned the reason for this is that it produces $\ce{OH-}$ ions in water. They stated this reaction:
$\ce{NH3 + H2O -> NH4OH}$
So That's why, they said that it is a base.
But in a neutralization reaction, mentioned by our teacher,
Acid + Base = Salt + water
So, if $\ce{NH3}$ is a base then, it should be,
Acid + $\ce{NH3}$ = Salt + Water
But it does not happen. When reacting with acid, it doesn't produce water.
For example,
$\ce{NH3 + HCl -> NH4Cl}$
-- Reference
Again,
$\ce{NH3 + H2SO4 -> (NH4)2SO4}$
-- Reference
So it is not producing water in the neutralization reaction. Hence, I'm confused whether it is base or not.