Many of you may have noticed that the Russian modal “verb” должен (must/have to) has an unusual conjugation in all tenses. In this post, we will clarify that grammar aspect.

To be honest, everything is much easier than you could expect. The word должен grammatically is a typical short form of adjective. That’s why it has only four forms: masculine, feminine, neuter and plural.

Modal "verb" MUST/HAVE TO in Russian

Должен is always followed by an infinitive form of a verb. An aspect of the verb could be either Imperfective or Perfective. And we apply the general rule of the verb aspects.

Я должен купить свёклу, потому что сегодня вечером буду готовить борщ.I have to buy a beetroot because I’m cooking borsch tonight.
Купить is a perfective form because the action will happen once and highly presumably there will be a result. Compare with:
Я должен покупать хлеб каждое утро, потому что моя семья любит свежий мягкий хлеб.I have to buy bread every morning because my family loves fresh fluffy one.
Покупать is an imperfective form as there is the indication to regularity (каждое утро).

In past tense, we add был if the subject is masc. sing., была is for fem. sing., было is for neut. sing., and были when it is plural.

Мы должны были закупиться консервами раньше.We had to purchase canned food earlier.
Она должна была прочитать эту статью.She had to read that article.
Кафе должно было открыться в 10 утра.The cafe had to be opened at 10am.
Ученики должны были написать пересказ этой истории.The pupils had to write the retelling of the story.
Сын должен был позвонить маме.Son had to ring his mum.

In future tense, we always conjugate the verb быть according to the subject it is used with.

Ты должна будешь парковаться только на этом парковочном месте.You will have to park at that parking space only.
Вы должны будете сдать книгу в библиотеку к следующей среде.You will have to drop off the book to the library by next Wednesday.
Мы должны будем закончить этот проект завтра.We will have to finish this project tomorrow.
Девочка должна будет делать домашнее задание на выходных.The girl will have to do homework on the weekend.
Я должна буду поменять колесо самостоятельно.I will have to change a tire on my own.

The negative form не должен means mustn’t, needn’t or don’t have to.

Ты не должна заводить крыс.You mustn’t have rats as your pets.
Они не должны были видеть это.They mustn’t have seen that.
Футболисты не должны будут играть два дня подряд.The footballers didn’t have to play two days in a row.
Я не должен говорить об этом.I mustn’t have told about that.

If to say shortly, this grammar topic is relatively easy but extremely important both for communication and understanding announcements at any public places.

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