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Questions & Answers about Зимние ботинки должны быть тёплыми и непромокаемыми.
What is the function of должны быть in this sentence?
It’s a modal construction combining:
- должны (plural of должен): expresses obligation (must or should)
- быть: the infinitive to be
Together должны быть means must be or should be, indicating that winter boots are required to have certain properties.
Why are тёплыми and непромокаемыми in the instrumental case?
In Russian, when a predicate adjective follows a linking verb like быть, it takes the instrumental case. Since ботинки is plural, the adjectives become plural instrumental: тёплыми and непромокаемыми.
Why are the adjectives in plural form?
Adjectives in Russian agree with the noun they modify in number, gender and case. Ботинки (boots) is a plural noun, so its predicate adjectives also appear in plural.
Could we use the adjectives in the nominative case here, like тёплые and непромокаемые?
Not after быть as predicates. If you want to place them before the noun attributively, you’d use nominative plural:
- тёплые и непромокаемые ботинки (warm and waterproof boots)
But following быть, they must be instrumental.
Can we use short-form adjectives instead: тёплы and непромокаемы?
Yes. You could say:
- Зимние ботинки должны быть тёплы и непромокаемы.
Short-form adjectives are grammatically correct here but give a slightly more concise or stylistic tone.
What does непромокаемыми mean and how is it formed?
- непромокаемыми means waterproof (literally “not soaking-through”).
- It’s formed from the imperfective verb промокать (to get wet) + participial/adjectival suffix -аемый
- negation prefix не-.
- In plural instrumental, it appears as непромокаемыми.
How do you pronounce непромокаемыми, and where is the stress?
It’s pronounced ne-pra-mo-KÁ-ye-mi-mi, with the stress on the ка́е syllable: непромокáемыми.
Is there a difference between непромокаемыми and водонепроницаемыми?
- Both mean waterproof or water-impermeable.
- непромокаемый focuses on not letting water soak in (commonly used for clothing and shoes).
- водонепроницаемый literally means “impermeable to water” (often used for materials, containers or structures).
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