辛い

1. Origins, structure, and basic meaning

• Structure: 辛い, read つらい, is an i-adjective meaning emotionally painful or difficult to endure.
• Basic usage: 別れは辛い describes emotional pain; 作業を続けるのは辛かった describes a difficult task in the past.

2. Common pitfalls and similar expressions

• Emotional pain and practical difficulty
  • Parting selects painful, while prolonged unfamiliar work selects difficult; the past replaces final い with かった.