永久

1. Origins, structure, and basic meaning

• Structure: 永久 is read as えいきゅう and is a noun for permanence or continuation without an end.
• Basic usage: It becomes adverbial in 永久に刻まれる and forms the compound 永久保存.

2. Common pitfalls and similar expressions

• Adverbial form with に
  • 永久に describes the wish as being engraved forever.
• Scope of preservation wording
  • 永久保存する資料 identifies material designated for permanent preservation; the sentence does not prove literal survival forever.