～ない

1. Origins, structure, and basic meaning

• Structure: Add ない to the negative stem required by the verb class.
• Basic usage: It negates a habit or future action in plain style, as in 夜はコーヒーを飲まない。.

2. Common pitfalls and similar expressions

• Stems by verb class
  • Godan verbs change as in 飲む → 飲まない, and ichidan verbs as in 食べる → 食べない. Also distinguish 買う → 買わない and the irregular forms する → しない and 来る → 来ない（こない）.
• Past forms and noun modification
  • The past negative is 飲まなかった. The plain negative can also directly modify a noun, as in 肉を食べない人.