Inattention; lack of focus where attention wanders, often causing problems in study, work, or driving.
彼は注意力散漫で授業中にすぐぼんやりしてしまう。
He is inattentive and quickly becomes absent-minded during class.
運転中の注意力散漫は重大な事故につながりかねない。
Inattention while driving can lead to serious accidents.
長時間の単純作業で注意力散漫になりやすいので、こまめに休憩をとった方がいい。
You tend to lose focus during long repetitive tasks, so it's better to take frequent breaks.