役立つ

1. Origins, structure, and basic meaning

• Structure: 役立つ (やくだつ) is an intransitive verb meaning to be useful for a purpose. The examples show realized benefit and general utility.
• Basic usage: Travel expressions proved useful at work; a checklist helps when gathering tools.

2. Common pitfalls and similar expressions

• Knowledge that proved useful and list intended to assist
  • Useful subjects are 表現が and 一覧は; settings are 仕事でも and ときに. The verb does not directly take a person as object.