もう〜た／〜ている

1. Origins, structure, and basic meaning

• Structure: Use もう with a verb's た form or a ている form expressing a resulting state.
• Basic usage: It indicates that an event has already finished or its resulting state has been reached by the reference time.
  • 宿題はもう終わっています。 means that the homework is already finished.

2. Common pitfalls and similar expressions

• Progress and resulting state
  • In もう完成しています, ています describes a completed state here, not an ongoing act of construction. Not every ている form means an action is in progress.
• When something is not finished yet
  • Use an expression such as まだ終わっていません for something not yet finished. Keeping もう and simply negating the verb does not give the same meaning.
• もう with a negative
  • もう行きません can mean that someone will not go anymore. This is not the completed-action meaning of having already gone.