Questions & Answers about Kirjekuori puuttuu, joten en voi lähettää kirjettä.
With puuttua (to be missing / to be lacking), the thing that is missing is typically the subject, so it appears in the nominative:
- Kirjekuori puuttuu. = An envelope is missing.
Another common structure is to mark who is lacking something:
- Minulta puuttuu kirjekuori. = I’m missing an envelope / I don’t have an envelope.
So kirjekuori is treated as the grammatical subject of puuttuu.
Puuttuu is the 3rd person singular present tense form of puuttua.
- puuttua = to be missing; to be lacking; to be absent
- (se) puuttuu = it is missing
It’s an intransitive verb here (no direct object).