Адвокат проверил документ.

Адвокат is in the nominative case, which is the case typically used for the subject of the sentence.

In Адвокат проверил документ, адвокат is the person who performed the action, so nominative is the expected form.

A few useful details:

• адвокат is a masculine noun
• its dictionary form is also адвокат
• in this sentence, it means the subject: the lawyer / attorney

So the sentence structure is:

• Адвокат = subject
• проверил = verb
• документ = object

Yes, the direct object is in the accusative case here. The reason it still looks like документ is that for many inanimate masculine singular nouns, the accusative form is identical to the nominative form.

So:

• nominative: документ
• accusative: документ

That is completely normal.

Compare:

• Я вижу документ. = I see the document.
• Документ лежит на столе. = The document is lying on the table.

In both examples, the form is документ, but the case is different based on its role in the sentence.

Проверил is the past tense, masculine singular form of the verb.

It agrees with the subject адвокат, which is grammatically masculine singular.

Russian past tense works like this:

• проверил = masculine singular
• проверила = feminine singular
• проверило = neuter singular
• проверили = plural

So if the subject changed, the verb would change too:

• Адвокат проверил документ.
• Адвокатка / женщина-адвокат проверила документ.
• Адвокаты проверили документ.

Проверил is the perfective past tense form of проверить.

Perfective verbs usually present an action as:

• completed
• finished
• viewed as a whole

So проверил документ suggests that the lawyer checked the document and completed that action.

The imperfective partner is проверял (from проверять).

Compare:

• Адвокат проверил документ. = The lawyer checked the document.
  -> completed action

• Адвокат проверял документ. = The lawyer was checking the document / checked the document (process, repeated, or without focus on completion)

This is a very common Russian contrast.

The stress is:

• адвокАт
• провЕрил
• докумЕнт

So one helpful pronunciation guide is:

• ad-va-KAT pra-VYE-ril da-ku-MYENT

A few pronunciation notes:

• Unstressed о often sounds closer to a in normal speech.
• Russian stress is important because it is not always predictable.
• Learning the stressed syllable together with each new word is a very good habit.

Russian does not have articles like a, an, or the.

So Адвокат проверил документ can mean:

• The lawyer checked the document
• A lawyer checked a document
• sometimes The lawyer checked a document, etc.

The exact interpretation depends on context.

Russian usually expresses definiteness and indefiniteness through:

• context
• word order
• intonation
• additional words if needed

The default neutral order here is:

• Адвокат проверил документ.

That is a normal subject-verb-object order.

But Russian word order is more flexible than English because the case endings help show each word’s role.

For example, you could also say:

• Документ проверил адвокат.

This still means The lawyer checked the document, but the emphasis changes. It may sound like you are focusing on who checked the document, or contrasting it with something else.

So:

• Адвокат проверил документ. = neutral statement
• Документ проверил адвокат. = more marked, emphasis on адвокат

Grammatically, адвокат is a masculine noun, and in this sentence the verb проверил also shows masculine agreement.

In traditional usage, адвокат can refer to the profession in general, but when talking about a specific woman, modern Russian may use either:

• адвокат with feminine context elsewhere
• or a feminine form in some contexts, depending on style and speaker preference

For a beginner, the key point is:

• in Адвокат проверил документ, the grammar clearly points to a masculine singular subject

If the sentence referred to a woman, you would most likely see:

• Адвокат проверила документ.

because the past tense verb would change to feminine.

The dictionary form is проверить.

That is the infinitive, meaning to check / to verify.

So the forms are related like this:

• проверить = infinitive
• проверил = past masculine singular
• проверила = past feminine singular
• проверили = past plural

It is useful to learn verbs in pairs when possible:

• проверять = imperfective
• проверить = perfective

That will help you understand both tense and aspect more naturally.