Russian Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Russian language. It only takes a minute to sign up.
Sign up to join this community
What is the difference between "мне нельзя" and "я не могу"? Both they means "I cannot"?
For example: "мне нельзя курить" and "я не могу курить" both meaning "I cannot smoke"? In some phrases I saw "нельзя" used like "it's forbidden", but in some other phrases seems used just like "cannot".
In general:
"мне нельзя" - i was forbidden to do something
“я не могу” - i cannot do something
In case they are interchangeable:
It is true that in some cases they are interchangeable.
In your example:
1 - "мне нельзя курить потому что я болею", 2 - "я не могу курить потому что я болею" would have very similar meaning, however if I heard someone say ex. 1 without any context I would assume that he has some medical condition and he can not smoke ever, and in ex 2 I would assume that he has some cold and can't smoke right now (maybe next couple of days).
So to be more general if duration is not specified explicitly and meaning is interchangeable "мне нельзя" would mean long term (possibly forever) while “я не могу” would refer to some shorter period of time
In a nutshell - people use "мне нельзя" when they want to say: "I'd like to, but there would be severe repercussions".
"Я не могу" is more generic.
I would say, "Мне нельзя" means some external restriction, most often - "I was forbidden", but also may be medical condition. It's not "I cannot", rather "I should not" or "I must not". "Я не могу" is more general and may also mean "I'm not able for", or "I cannot" without specifying the reasons.
"Мне нельзя курить" sounds like a medical condition (I have an ulcer, I should not smoke), but may also be a restriction. "Я не могу курить" sounds really strange, like "I am not able to" (I tried, but I start caughing so badly I have to stop right away?).
I would not agree with Alexander that "нельзя" carries that "I want to" connotation internally, although it may widely be used that way (you don't want to refuse blatantly, so you refer to some external cause).
