Iemand heeft de deur open gelaten.
English: Someone left the door open.
Indefinite pronouns are words in Dutch that refer to people or things in a general, non-specific way. They do not name a specific person or object.
Use indefinite pronouns in Dutch when you want to talk about someone or something in a general sense, without being specific. They are useful when you do not know or do not want to say exactly who or what you mean.
Iemand heeft de deur open gelaten.
English: Someone left the door open.
Heb je iets nodig?
English: Do you need something?
Niemand weet het antwoord.
English: No one knows the answer.
Alles is klaar voor het feest.
English: Everything is ready for the party.
Sommige mensen houden van koffie.
English: Some people like coffee.