Soundness: A proof system is sound (or correct) if all of its rules are sound, whenever $A_1, ..., A_n \vdash B$ then $A_1, ..., A_n \models B$.
Soundness: A proof system is sound (or correct) if all of its rules are sound, whenever $A_1, ..., A_n \vdash B$ then $A_1, ..., A_n \models B$.