Через неделю мне исполнится двадцать лет.

In a week I will turn twenty years old.

Breakdown of Через неделю мне исполнится двадцать лет.

• год: the year
• мне: me
• через: in
• неделя: the week
• двадцать: twenty
• исполниться: to turn (years old)

Questions & Answers about Через неделю мне исполнится двадцать лет.

What does через неделю mean here, and what case is неделю in?

Через неделю means “in a week / a week from now” (counting forward from the present).

Literally, через can mean “through” or “across”, but with time it means “after, in (a certain amount of time)”.

Grammar:

• через
  • accusative case = “in / after (a period of time)”
    
    • через час – in an hour
    • через месяц – in a month
    • через неделю – in a week

So неделю is accusative singular of неделя (“week”), required by the preposition через.

Why is it мне and not я? What case is that?

Мне is dative case of я (“I”).

In Russian, age is usually expressed with a dative “experiencer,” literally:
“To me will be fulfilled twenty years.”

So:

• мне – to me (dative)
• ему – to him
• ей – to her

Common age patterns:

• Мне двадцать лет. – I am twenty (to me [there are] twenty years).
• Через неделю мне исполнится двадцать лет. – In a week, I will turn twenty (to me will be fulfilled twenty years).

Using я would be ungrammatical here; with age you almost always see мне / тебе / ему / ей / нам / вам / им.

What exactly does исполнится mean, and why does it have -ся at the end?

Исполнится is the 3rd person singular future of the verb исполниться (perfective aspect).

Basic meanings of исполниться:

1. To be fulfilled / to be completed (literally or figuratively)
2. (About age or terms): for a certain amount of time/years to be completed → for someone to reach a certain age

So in age expressions, исполниться roughly corresponds to:

• “to turn (a certain age)”
• “to reach (a certain age)”

The -ся ending marks it as a reflexive / middle-voice verb. Many Russian verbs that describe states “happening” or “coming about” to someone use -ся, and they are often translated into English with a simple active verb:

• Мне исполнится двадцать лет. – I will turn twenty.
• Срок исполнения договора истечёт. – The term of the contract will expire.

Here, исполнится is not “I will fulfill (something)” but rather “(my twenty years) will be completed (to me)”.

Why is исполнится in the future tense when we already have через неделю (“in a week”)? Isn’t that redundant?

No, it’s not redundant. Each element does a different job:

• через неделю tells when – the time frame: in a week.
• исполнится is the main verb in the future tense: will be fulfilled / will turn.

Russian still needs a future tense verb to show that the action happens in the future. Compare:

• Сейчас мне двадцать лет. – Now I am twenty.
• Через неделю мне исполнится двадцать лет. – In a week I will turn twenty.

Just like in English you say “In a week I will turn twenty”, not “In a week I turn twenty” (except in specific stylistic contexts).

Why is it двадцать лет and not двадцать года?

The noun год (“year”) changes after numbers. This is one of Russian’s standard “number + noun” patterns:

• 1 год – one year
• 2, 3, 4 года – two / three / four years
• 5–20 лет – five to twenty years

Then it repeats by the last digit:

• 21 год
• 22, 23, 24 года
• 25–30 лет

So:

• 20 ends in 0 → treated like the “5–20” group → use лет.
• двадцать лет is therefore the correct form.

Лет here is the genitive plural of год, used after numbers 5 and higher (and any number ending in 5–9 or 0, except for the teens 11–14, which also use лет).

Why does the verb исполнится look singular even though двадцать лет seems plural?

In Russian, when the subject is a numeral phrase like двадцать лет, the verb is usually in neuter singular, especially when the number is treated as a single amount of time/quantity.

So:

• Исполнилось двадцать лет. – Twenty years passed / it has been twenty years.
• Исполнится двадцать лет. – Twenty years will be fulfilled / It will be twenty years.

You can think of двадцать лет here as “one 20‑year period,” and Russian matches the verb in the standard default form (3rd person singular neuter).

This is normal with many expressions where the “subject” is a measure or quantity:

• Прошло три дня. – Three days passed.
• Осталось пять минут. – Five minutes remain.

The singular verb is correct and idiomatic.

Is Через неделю мне исполнится двадцать лет formal, neutral, or casual? How else can I say “I’ll turn twenty in a week”?

Через неделю мне исполнится двадцать лет is neutral, maybe slightly on the formal / careful side, because of the verb исполнится.

Common alternatives:

• Через неделю мне будет двадцать лет.
  Literally: “In a week, it will be twenty years to me.”
  – Very common, neutral everyday speech.

• Мне через неделю будет двадцать лет.
  – Same meaning, different word order.

More colloquial:

• Через неделю мне стукнет двадцать. – Slangy: “I’ll hit twenty / I’ll be hitting twenty.”

So, for everyday use, мне будет двадцать лет is extremely common; мне исполнится двадцать лет sounds a bit more formal, “correct,” or written-style.

Can I change the word order? For example, can I say Мне через неделю исполнится двадцать лет?

Yes. Russian word order is fairly flexible. All these are grammatically correct:

• Через неделю мне исполнится двадцать лет.
• Мне через неделю исполнится двадцать лет.
• Мне исполнится двадцать лет через неделю.

Nuance:

• Putting через неделю at the beginning (Через неделю…) makes the time the main focus: As for a week from now…
• Putting мне first (Мне через неделю…) emphasizes “for me” / “as for me”*.
• Ending with через неделю can sound like the time information is added after emphasizing the age itself.

For a learner, the original sentence order is the most neutral and easy to imitate.

What is the difference between через неделю and something like спустя неделю or через одну неделю?

All are related but slightly different in feel.

1. через неделю – the most common, neutral:

   • Через неделю мне исполнится двадцать лет. – In a week I’ll turn twenty.

2. спустя неделю – also “after a week,” but a bit more narrative/written, less colloquial:

   • Спустя неделю мне исполнится двадцать лет. – After a week, I’ll turn twenty.
     Often used in storytelling about the past or future sequences.

3. через одну неделю – adds emphasis on “one week” (and can sound a bit heavy or overly precise in everyday speech):

   • Через одну неделю мне исполнится двадцать лет. – In exactly one week I’ll turn twenty.

In normal conversation, через неделю is what you should default to.

Could I just say Через неделю мне будет двадцать and drop лет?

Yes, in informal speech Russians often drop лет when the context is clear:

• Через неделю мне будет двадцать. – In a week I’ll be twenty.
• Мне двадцать. – I’m twenty.

However, the full form двадцать лет is always correct and is preferred in formal or careful speech:

• Через неделю мне исполнится двадцать лет. – fully explicit, stylistically neutral/formal.

As a learner, using лет is always safe; omitting it is fine in casual conversation once you feel comfortable.