Passive infinitive (должен быть, может быть)

The Passive Infinitive

To state that something must be done or can be done, Russian uses a modal word, the infinitive быть (to be), and a short past passive participle.

Must Be (Должен быть)

To say something "must be" done, use the short adjective должен (must/obliged) + быть + a short past passive participle.

Because должен and the participle act like adjectives, both must agree with the gender and number of the subject:

  • Masculine: должен / осмотрен
  • Feminine: должна / закреплена
  • Neuter: должно / сделано
  • Plural: должны / пристёгнуты

Can Be / Might Be (Может быть)

To say something "can be" or "might be" done, use the verb может (singular) or могут (plural). Since this is a conjugated verb, it changes for number but not for gender. The short participle at the end, however, still matches the gender and number of the subject.

Negation

Negation works exactly as you would expect: simply place не directly before the modal word.