expression
usually; normally; under normal circumstances
Sets up a contrast between what normally happens and a specific exception or hypothetical situation. Often followed by 〜が, 〜けど, or 〜のに.
通常なら10分で着くが、今日は渋滞で30分かかった。
Normally it takes 10 minutes, but today it took 30 minutes because of traffic.
通常ならありえないミスだ。
It's a mistake that would normally be unthinkable.
Compound of 通常 (tsuujou, 'usual, normal') + なら (nara, conditional form of the copula だ). Literally 'if it is usual'.