泡立つ

1. Origins, structure, and basic meaning

• Structure: 泡立つ is read as あわだつ and means “to foam” and “to froth”.
• Basic usage: It describes soap foaming white in water and seawater frothing violently along the shore.

2. Common pitfalls and similar expressions

• Key distinction: 石けんが泡立つ
  • It describes soap or water becoming foamy, not someone foaming it, so the foaming substance is the subject as in 石けんが泡立つ.