why ammonia and borontri flouride form adduct easily?what is an adduct?

N in ammonia has a lone pair of electrons hence can act as a Lewis base.B in borontrifloride has a vacant p orbital hence can act as a Lewis acid. There is formation of a coordinate bond between lone pair of N and vacant orbital of B leading to formation of an adduct.

Adduct is an addition product of a reaction between different molecules wherein the product contains all atoms of the reacting species.Such reactions yield single products.