secret · dense

1. Origins, structure, and basic meaning

• Structure: 密 conveys density or secrecy.
• Basic usage: 密集（みっしゅう） means being densely gathered, while 秘密（ひみつ） means a secret kept from others.

2. Common pitfalls and similar expressions

• Density, secrecy, and a small kana
  • 密集 is used for closely packed houses or people crowded together. Its reading, みっしゅう, contains a small っ.
  • 秘密にしておこう means let's keep it secret. In 秘密, 密 is read みつ, and the word refers to concealed information rather than a crowded space.