Learn Hardcore Russian: Сон помогает восстановить силы после долгого дня. - Sleep helps restore strength after a long day.

сон is a noun (masculine, singular). In this sentence it acts as the subject—the “doer” of the action—so it appears in the nominative case (the default case for subjects in Russian).

Why is помогает used with the infinitive восстановить, and not with a conjugated verb form?

In Russian, verbs meaning “to help” (помогать/помочь) are typically followed directly by an infinitive to show what action is being helped. Here помогает восстановить literally means “helps [to] restore.” You almost never say помогает мы восстанавливаем, you use the infinitive.

Why is восстановить in the perfective aspect rather than the imperfective восстанавливать?

Perfective aspect (восстановить) emphasizes the completion of an action—in this case, fully regaining your strength. The imperfective (восстанавливать) would focus on the process without guaranteeing completion (“helps to be restoring strength,” which sounds awkward).

What case is силы, and why is it used here?

силы is the accusative plural form of сила (“strength, energy”). It’s the direct object of the infinitive восстановить—what is being restored. Since сила is an inanimate feminine noun, its accusative plural is identical to the nominative plural силы.

Why does the preposition после take долгого дня in the genitive case?

By rule, после always governs the genitive case to indicate “after” something. Hence после долгого дня (“after a long day”) uses the genitive singular of день.

Why is день changed to дня, and why is the adjective долгого also in that form?

дня is the genitive singular of день. Adjectives must agree with their nouns in gender, number, and case, so долгого is the genitive singular masculine form of долгий.

Can I change the word order to say После долгого дня сон помогает восстановить силы?

Yes. Russian has relatively flexible word order for emphasis. Moving после долгого дня to the front highlights “after a long day,” but the core meaning remains the same.

Could I use the verb спать instead of сон to form a similar sentence? For example, Спать помогает восстановить силы после долгого дня.

You can, but it shifts the emphasis. Спать помогает… (using the verb “to sleep”) highlights the action of sleeping, whereas сон помогает… (using the noun “sleep”) presents sleep more as an abstract concept or state. Both are grammatically correct.

What is the stress pattern in сон помогает восстановить силы после долгого дня?

The main stresses are on сон, помогáет (second syllable), восстановúть (third syllable), and дóлгого (first syllable). So: сон помогáет восстановúть силы после дóлгого дня.