流れ

1. Origins, structure, and basic meaning

• Structure: 流れ is read as ながれ and means either physical flow, such as moving water, or the course and trend of events, discussion, or an era.
• Basic usage: Use 川の流れ for the physical current of a river and 議論の流れ for the course of a discussion.

2. Common pitfalls and similar expressions

• Difference between 流れ and 流行
  • The former is a continuing direction ranging from water flow to a discussion's course or a broader trend, whereas the latter is temporary widespread popularity or fashion.