"I do not know if he is home."
Translation:Ik weet niet of hij thuis is.
Why is this 'of' and not 'als' for if? Is "Ik weet niet als hij thuis is" wrong? Thanks
That's because in this case "if" has the sense of "whether". Thus we use "of" instead of "als".
But I would say that "I don't know if he is home" and "I don't know whether he is home" were equivalent in English, I would use them interchangeably. I still don't get the distinction here.
The English word "if" is used in two different ways. Firstly, it can be used to mean "whether", like in this sentence. You are right, "if" and "whether" are completely interchangeable here. That is when Dutch uses the word "of".
Secondly, it can be found at the start of conditional subclauses. You could replace it with "provided that" or "in the case that" or sometimes just with "when", but not with "whether". In that case, Dutch uses "als". For example:
- If it rains, I do not go outside. - Als het regent, ga ik niet naar buiten.
- I go if you are going too. - Ik ga als jij ook gaat.
weten is about facts, you know whether he is home or not. Kennen refers more to be acquainted with someone
I believe you could use both, yet 'zit' doesn't get used as much as 'is', since it is a bit less polite to use.
Because you cannot place niet between the subject and verb in a main clause.