一生

1. Origins, structure, and basic meaning

• Structure: 一生 (いっしょう) is a word for a person’s entire lifetime, used adverbially or as a nominal object.
• Basic usage: 一生忘れない adverbially sets the duration of never forgetting, while 一生を教育に捧げる makes an entire life the object devoted to education.

2. Common pitfalls and similar expressions

• Bare duration and を-marked object
  • In 一生忘れない, 一生 is unmarked and gives the duration of the action. In 一生を捧げる, を marks it as a noun phrase, so the syntactic roles differ.