重なる

1. Origins, structure, and basic meaning

• Structure: 重なる (かさなる) is an intransitive verb for schedules overlapping or small effects accumulating together.
• Basic usage: 日程が重なった reports a meeting and trip overlapping in time, while 努力が重なれば states a condition in which small efforts accumulate.

2. Common pitfalls and similar expressions

• Scheduling overlap and accumulation
  • 日程が重なる is a timing conflict, whereas 努力が重なる figuratively accumulates repeated effects. Neither is a transitive action in which someone deliberately stacks schedules.