収入

1. Origins, structure, and basic meaning

• Structure: 収入 (しゅうにゅう) is a noun for money received over time from work or other earning activity.
• Basic usage: 毎月の収入から貯金する marks income as the source of savings, while 収入が増える makes earnings the subject that rise after starting a side job.

2. Common pitfalls and similar expressions

• Income and the amount saved
  • In 収入から一定額を貯金する, not all income is saved; only a fixed portion is taken from it. 収入 and 貯金 are not the same amount.