そうだ

1. Origins, structure, and basic meaning

• Structure: そうだ after a plain-form statement reports information from another person or the media, retaining present affirmative だ with nouns and na-adjectives.
• Basic usage: 友人の話では、その店は閉店したそうだ。 reports the store's closure on the basis of information from a friend.

2. Common pitfalls and similar expressions

• Hearsay versus appearance
  • 雨が降るそうだ reports having heard that it will rain, while 雨が降りそうだ describes signs or an appearance of imminent rain. The dictionary form versus the masu-stem separates reporting from an appearance-based judgment.
• Negation and past time belong to the reported content
  • 休みではないそうだ reports that it is not a day off, while 休みだったそうだ reports that it was one. First put negation or past time into the reported statement, then add そうだ.