内心

1. Origins, structure, and basic meaning

• Structure: 内心, read ないしん, refers to thoughts or feelings held inwardly and can function adverbially.
• Basic usage: It describes private anxiety concealed behind calm behavior or envy felt without being openly expressed.

2. Common pitfalls and similar expressions

• Feelings not shown outwardly
  • It denotes anxiety or envy felt inwardly while not necessarily shown. It contrasts with feelings openly expressed in words or facial expression.