損

1. Origins, structure, and basic meaning

• Structure: 損 (そん) denotes loss or disadvantage. 損をする presents a loss being incurred; 損ではない negates the judgment that something is a loss.
• Basic usage: Buying an unnecessary item becomes a disadvantage, while a detour with enjoyable scenery is judged not to be one.

2. Common pitfalls and similar expressions

• Loss incurred and negative value judgment
  • Idiomatic 損をする means to suffer a loss, whereas 損ではない evaluates the tradeoff after considering a benefit. Keep the を construction separate from the predicative form.