Вчера я посетил Большой театр.

Yesterday I visited the Bolshoi Theatre.

Breakdown of Вчера я посетил Большой театр.

• я: I
• вчера: yesterday
• посетить: to visit
• Большой театр: Bolshoi Theatre

Questions & Answers about Вчера я посетил Большой театр.

Why do we use посетил instead of посещал?

посетил is the perfective past of посетить, which describes a single, completed action (“I visited the Bolshoi Theatre once, and finished that visit”).
посещал is the imperfective past of посещать, implying repeated or continuous visits over time (“I used to visit…, I was visiting…”). Since you mean “I went and completed that visit yesterday,” you choose the perfective посетил.

Why doesn’t Большой театр change its form after посетил?

In this sentence Большой театр is the direct object of a transitive verb and thus is in the accusative case. For most masculine inanimate nouns the accusative singular is identical to the nominative singular. That’s why Большой театр stays unchanged.

Why isn’t there a preposition в before Большой театр?

The verb посетить directly takes its object without a preposition. You say посетил музей, посетил концерт, посетил Большой театр. If you used в, you’d need a different verb, for example сходил в Большой театр (“went to the Bolshoi Theatre”).

Can you move Вчера to a different position in the sentence?

Yes. Russian word order is relatively flexible. You could also say:

• Я вчера посетил Большой театр. (neutral)
• Я посетил Большой театр вчера. (puts a bit more focus on what you visited)
• Вчера я посетил Большой театр. (emphasizes “yesterday” as the time)
  The meaning stays the same, though the element you place first often gains emphasis.

Why is я included? Could we omit it?

Russian allows dropping subject pronouns when the verb ending clearly indicates the subject. Because посетил ends in -ил, it signals я/он (I/he) in the past. You could say simply Вчера посетил Большой театр, and a Russian speaker would understand you meant “I visited….” Including я adds clarity or emphasis but isn’t grammatically required.

How would this sentence change if the speaker were female?

In the past tense, the verb agrees with the speaker’s gender. A female would say:
Вчера я посетила Большой театр.
Here посетила (ending -ла) marks the feminine singular.

Why is only Большой capitalized and not театр?

In Russian, when a proper name consists of a generic noun plus a distinctive word, only the first word is capitalized.
Thus:

• «Большой театр» (Большой is capitalized; театр is a common noun)
• «Казанский Кремль» (Казанский – proper adjective; кремль – generic noun)

Where is the stress in Большой театр and how do you pronounce it?

• большо́й – stress on the second о: bal-SHOY
• теа́тр – stress on а: tee-Á-tr
  Phonetically: [balˈʂoj tiˈatr].