遊ぶ

1. Origins, structure, and basic meaning

• Structure: 遊ぶ (あそぶ) combines play stem 遊 with inflecting ぶ as the verb for playing or spending leisure time.
• Basic usage: 遊ぶ is the dictionary form for playing or spending leisure time, while 遊んでいた presents that activity as ongoing over a period in the past.

2. Common pitfalls and similar expressions

• Dictionary form and past progressive
  • The subject need not be a child.