まだ〜ていない

1. Origins, structure, and basic meaning

• Structure: Combine まだ with a verb's て form followed by いない. The polite form is ていません.
• Basic usage: 朝ご飯はまだ食べていません。 says that breakfast has not been eaten by the reference time.

2. Common pitfalls and similar expressions

• Noncompletion and intention
  • まだ食べていない describes not having eaten yet, while まだ食べない can mean choosing not to eat for now. Distinguish completion from a choice about a forthcoming action.
• Reference time
  • その時はまだ見ていなかった describes not having seen something by that past moment. It does not alone determine whether it was seen later.