This is the 7666th most frequent Japanese word.
区別
Distinction; differentiation.
区別 is used to refer to the differentiation between moral concepts: good and evil.
子供たちに善悪の区別を教えるのが大切です。
It is important to teach children the distinction between right and wrong.
区別 applies to the ability to perceive and differentiate colors visually.
目が悪くて色の区別ができません。
I have poor eyesight and cannot distinguish between colors.
区別 signifies the separation of concepts or activities, in this case, work and leisure.