元

1. Origins, structure, and basic meaning

• Structure: It is read もと. This word refers to a former state or the origin from which something develops.
• Basic usage: It explains a museum building's former use or the event that provided the basis for a story.
  • この建物は元は郵便局で、今は小さな美術館になっている。

2. Common pitfalls and similar expressions

• A former state and an origin
  • 元は郵便局 has a temporal meaning: the building used to be a post office.
  • 話の元 refers to the event or source from which the story developed.