筋

1. Origins, structure, and basic meaning

• Structure: The single kanji 筋, read すじ, denotes a bodily or narrative line.
• Basic usage: 筋 can refer to a muscle or tendon, or to the line of a story or argument.

2. Common pitfalls and similar expressions

• Muscle and narrative line
  • Predicates after 筋を or 筋が distinguish a bodily context from a narrative or logical one.