Questions & Answers about Сегодня мне нужно работать дома.
Why is it мне нужно and not я нужно?
Russian uses a special “impersonal” construction for I need to do X:
- Мне нужно работать literally: To me it-is-necessary to work.
- мне is in the dative case and shows who has the need.
- нужно is a neutral, impersonal word meaning necessary. It doesn’t agree with я; it just stays нужно.
You cannot say я нужно работать; that’s ungrammatical. With нужно (in this sense), the “person” must be in the dative: мне, тебе, ему, нам, etc.
What case is мне, and what does that case mean here?
Мне is the dative case of я (I → to me).
In this construction, the dative marks the person who experiences the necessity:
- Мне нужно работать – I need to work (literally: To me it is necessary to work).
- Тебе нужно работать – You need to work.
So the dative here answers “to whom is this necessary?” → to me.
What’s the difference between мне нужно работать and я должен работать?