Learn Hardcore Russian: Моя тётя живёт в этом доме уже тридцать лет. - My aunt has been living in this building for thirty years already.

So Моя тётя живёт в этом доме уже тридцать лет literally is “My aunt lives in this house already thirty years”, but in English we translate it as “has lived / has been living”.

If you said:

Моя тётя жила в этом доме тридцать лет.
→ She lived in this house for thirty years (implies this is in the past; she probably no longer lives there).

So живёт focuses on an ongoing situation that started in the past and continues now.

In English we say “for thirty years”. Why is there no word for “for”, and what does уже actually do here?

Two separate points:

No word for “for”
Russian often expresses duration with just a bare time phrase, without a preposition:
- Она живёт здесь тридцать лет. – She has lived here for thirty years.
- Он работал там пять лет. – He worked there for five years.
There is no preposition like для or на in this construction; you simply put the time expression after the verb.
Meaning of уже
уже = already.
It adds the nuance that this is a long, accumulated period up to now, often with a hint of “wow, it’s been that long already”:
- With уже: Моя тётя живёт в этом доме уже тридцать лет.
  → She has been living here already thirty years (emphasising how long it’s been).
- Without уже: Моя тётя живёт в этом доме тридцать лет.
  → Still “has been living … for thirty years”, but more neutral, less emotional.

Why is it тридцать лет and not тридцать года or тридцать годов?

This comes from how Russian combines numerals with the noun год (year):

1: один год
2–4: два / три / четыре года
5–20: пять … двадцать лет
Then the pattern repeats by the last digit:
- 21 год, 22 года, 25 лет, 30 лет, 31 год, etc.

Since 30 ends in 0, it belongs to the 5+ pattern, so you must use:

тридцать лет (not тридцать года)

Grammatically, лет here is the genitive plural form of год.
The form годов also exists but is rare and stylistic; you would not use it with a numeral like this.

What case is в этом доме, and why do we have этом and доме with different endings?

в этом доме is in the prepositional case (also called locative in many textbooks):

The preposition в meaning “in / inside”
- a location → normally takes the prepositional case.
дом (house) in the prepositional singular is в доме.
этот (this) is a pronoun that declines like an adjective; in the prepositional masculine singular it becomes этом.

So:

Noun: дом → в доме (prepositional singular, ending -е)
Demonstrative: этот → в этом (prepositional masculine singular, ending -ом)

They agree in gender, number, and case (masculine, singular, prepositional), but nouns and adjective‑like words simply have different standard endings in that case.

Is the word order fixed, or can we move уже тридцать лет or в этом доме to other positions?

Russian word order is more flexible than English. All of these are grammatically correct, with slightly different emphasis:

Моя тётя живёт в этом доме уже тридцать лет.
Neutral, common order; mild focus on уже тридцать лет at the end.
Моя тётя уже тридцать лет живёт в этом доме.
Highlights how long she has lived there; уже тридцать лет comes earlier.
Уже тридцать лет моя тётя живёт в этом доме.
Stronger emphasis on уже тридцать лет (“For thirty years already…”).

The basic meaning (who, where, for how long) does not change, but the part placed closer to the beginning often gets more emphasis or contrast.

Why is it моя тётя and not мой тётя? What gender is тётя?

тётя (aunt) is a feminine noun in Russian. Most nouns ending in -а or -я are feminine, and тётя follows that pattern.

Possessive pronouns (like мой / моя) must agree in gender with the noun:

мой папа – my dad (masculine)
моя тётя – my aunt (feminine)

So you need моя тётя, not мой тётя.

I often see Russian texts write тетя instead of тётя. How important is the letter ё here?

The letter ё always represents the sound [yo], and it always carries the stress in the word. In тётя, the correct pronunciation is [тё́тя] (something like TYO-tya).

In many everyday Russian texts, ё is written as е, so you may see тетя instead of тётя. Native speakers know from experience that it must be pronounced with ё.

For you as a learner:

Pronunciation: always say [yo] where the dictionary shows ё.
Spelling: in most contexts, writing е instead of ё is tolerated, but textbooks and dictionaries write ё to help learners with stress and pronunciation.

Can we drop этот and just say Моя тётя живёт в доме уже тридцать лет?

Yes, but the meaning changes:

в этом доме – in this house, a specific house already known from context or visible to the speakers.
в доме – in a house / in the house in a more general or less specific way (it could be understood as “in the house” if the context makes it clear which one, but there is no explicit this).

So:

Моя тётя живёт в этом доме уже тридцать лет.
→ My aunt has been living in *this (particular) house for thirty years.*
Моя тётя живёт в доме уже тридцать лет.
→ My aunt has been living in *a/the house for thirty years* (less specific; the exact house is not being pointed out).

Could this sentence ever refer to the future, like “My aunt will live in this house for thirty years”?

No. With живёт in the present tense plus a time period and especially уже, the sentence describes a period that started in the past and continues up to now.

To talk about the future, you would use the future tense and typically ещё (more / another) instead of уже:

Моя тётя будет жить в этом доме ещё тридцать лет.
→ My aunt will live in this house for another thirty years.

So the original sentence is firmly about past + present, not the future.