昔

1. Origins, structure, and basic meaning

• Structure: 昔 is read むかし.
• Basic usage: It refers to long ago or to a time in the past.

2. Common pitfalls and similar expressions

• Setting the time of a sentence
  • Sentence-initial 昔 places the whole event in the distant past.
• The past modifying a noun
  • 昔の学校 means schools as they were in the old days.