river

1. Origins, structure, and basic meaning

• Structure: 川 means a river or stream; its kun-reading is かわ and its on-reading is せん.
• Basic usage: 川(かわ) and 河川(かせん) both refer to rivers or waterways.

2. Common pitfalls and similar expressions

• Everyday language and river survey or management
  • 川 is the everyday word for a river. 水かさが増していた means the river's water level had risen.
  • 河川 is used in more formal contexts such as river surveys or management. 河川の水質 means the water quality of a river.