Completeness: A proof system is complete if whenever $A_1, ..., A_n \models B$, then $B$ can be derived from $A_1, ..., A_n$ using its inference rules.
Completeness: A proof system is complete if whenever $A_1, ..., A_n \models B$, then $B$ can be derived from $A_1, ..., A_n$ using its inference rules.