I am often confused by phrases like "не должен прочитать," "не должен сделать," "не должен работать," "не должен платить" and so on. Sometimes the negation appears to refer to "должен," and sometimes - to the subsequent verb (i.e., to "прочитать" or whatever follows after "должен"). That is, I often get confused as to which interpretation is correct - "is not obliged to read" or "is obliged not to read."

My question is this: Is there any simple rule or trick to determine which verb is implied to be negated in phrases like "не должен прочитать"?

There might be some rule I am not aware of. Or should I always assume that both interpretations are possible unless one of them is excluded by the context?

2 Answers 2


Usually (usually), imperfective means "should not be doing it":

Он не должен это читать // He cannot be required to be reading this

and perfective means "should be not doing it":

Он не должен это прочитать // He is not allowed to read that.

  • 1
    Ohh, so the key is in the aspect (perfective vs imperfective)! I had no idea it could be that simple.
    – Mitsuko
    Commented Jul 10, 2019 at 15:04
  • 1
    I just tried to recall numerous examples and feel that your rule is not universal. In particular, I recall something like "он не должен сейчас быть в университете, потому что сегодня выходной день." I now see two possible interpretations: (1) "He is not obliged to be in the university now, because today is a holiday." (2) "He is expected not to be in the university now, because today is a holiday." I am confused... This verb "должен" is already extremely tricky by itself, and now this ambiguity with the negation adds insult to injury...
    – Mitsuko
    Commented Jul 10, 2019 at 15:26
  • @Mitsuko: you're right, that's why I put the "usually" there twice.
    – Quassnoi
    Commented Jul 10, 2019 at 15:30

I would say - no trick needed. "(не должен) прочитать" has the same meaning as "должен (не прочитать)" - there is no differnce in result: you have an obligation to that book not to be read. There is no significant difference.

But if you want a rule - in general "is obliged not to read" is prefered in almoust any case ( when I translate Russuan to English I have to watch context of English phrase).

"Not obliged to read" should be translated to Russian as "не обязан читать"

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