Why formation of imines is a nucleophilic addition?

The initial attack is at the carbonyl carbon by a nucleophile (the amino nitrogen). This leaves the carbonyl oxygen with an anionic charge and it becomes protonated by the solvent. That is the nucleophilic addition part of the reaction and some of these reactions stop at that stage. Others like your example here continue by elimination of water to reform a double bond but this time a C=N double bond rather than the C=O you start with. So there are two classes of nucleophilic additions at a carbonyl group:
1. Those that stop at that stage and
2. Those that eliminate water to give an unsaturated product.

i don't know