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Voter maintenant !RéponduQuestion Linguistique
Hi, please what's the difference between "надо" & "должен", and when we use each of them ?

PS: Take a look at these free Russian educational resources: Free class: Perfective Imperfective — Greetings — Professions — Adjectives

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victor_onl profile picture victor_onlJuly 2019

If briefly:

it needs,  have a need, supposed to, =  надо
I need = мне надо
you need = тебе надо 
you supposed to be here at 7AM tomorrow, we'll get started  = Тебе надо быть здесь завтра в 7 утра, мы начнем.  

have to, must = должен 
I must = я должен
you must = ты должен

You must do your homework! = Ты должен делать домашнее задание!

and so on

Sultan_khan profile picture Sultan_khanJuly 2019
u can use word -должен- like owes something *for ex mp. you owe me money -ты должен мне денег . something like that or *have to or must *
(надо,нужно-need to)
_Greyhound_ profile picture _Greyhound_July 2019
Надо means necessity, need. It stands for things you need to do whatsoever. For instance, we all need food (otherwise we die). The closest word in English here is 'need' (as a verb).
Должен puports an obligation. Moral or external (so, должен is hereby a synonim to both 'must' and 'have to').