Месяц состоит из четырёх недель, а каждая неделя делится на семь дней.

A month consists of four weeks, and each week is divided into seven days.

Breakdown of Месяц состоит из четырёх недель, а каждая неделя делится на семь дней.

• день: the day
• состоять из: to consist of
• семь: seven
• месяц: the month
• а: and
• неделя: the week
• четыре: four
• каждый: each
• делиться на: to be divided into

Questions & Answers about Месяц состоит из четырёх недель, а каждая неделя делится на семь дней.

What does the verb состоять из mean, and why is it followed by из четырёх недель in the genitive case?

состоять из literally means “to consist of.” In Russian it is always used with the preposition из plus the genitive case. Hence:

• из (preposition) → governs genitive
• четырёх (genitive of четыре)
• недель (genitive plural of неделя)

So Месяц состоит из четырёх недель = “A month consists of four weeks.”

What does делиться на mean, and why is it followed by на семь дней in the accusative?

делиться на is a reflexive (middle-voice) verb meaning “to be divided into.” It always takes на + accusative when indicating division or splitting. Thus:

• на (preposition) → governs accusative
• семь (accusative of numeral “seven”; inanimate numerals 5+ look like nominative)
• дней (see next Q for why genitive plural appears)

So неделя делится на семь дней = “A week is divided into seven days.”

Why is the noun день in семь дней in genitive plural (дней) rather than nominative plural (дни)?

Russian numeral rules say:

• After numerals 5 and above, the counted noun takes the genitive plural form.
• Numeral семь itself remains unchanged in accusative (inanimate = nominative form).

Therefore семь дней is correct (not семь дни), even though на demands the accusative.

What is the role of the conjunction а between the two clauses, and how is it different from и or но?

The conjunction а here connects two related statements with a light contrast or transition.

• It’s softer than но (“but”) and doesn’t sound adversarial.
• It’s more contrasted than и (“and”), which simply links ideas without implying any shift.

So а signals “while/as for this other point,” fitting “…, а ….”

Why does делиться have the suffix -ся, and is this a passive construction?

The suffix -ся in делиться marks a reflexive/middle voice. Here it means “to divide itself,” i.e. “to be divided into.” Russian often uses this reflexive form instead of a separate passive verb or participle. Grammatically it behaves like a verb in the third person.

What nuance does adding каждая bring in а каждая неделя делится на семь дней, compared to simply неделя делится на семь дней?

Adding каждая (“each”) places emphasis on every single week individually. Without it, you’re stating a general fact about “the week” as a concept. With каждая неделя, you underline that every one of those four weeks follows the same division.

Could I rephrase it as Месяц делится на четыре недели, а неделя состоит из семи дней? Are there any differences in nuance?

Yes, that rephrasing is perfectly grammatical. The nuance shifts slightly:

• Месяц состоит из четырёх недель emphasizes composition (“what it is made of”).
• Месяц делится на четыре недели emphasizes the act of dividing.
  Likewise, неделя делится на семь дней stresses splitting the week, while неделя состоит из семи дней stresses its makeup. Both pairs are interchangeable with only a subtle change of focus.