Сотрудник проверил люк.

Проверил is the past tense form of the verb проверить.

The ending -л is the basic marker of past tense in Russian. In the singular, past tense also shows gender:

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

So here, проверил matches сотрудник, which is a masculine singular noun.

Because the subject, сотрудник, is a masculine noun.

In Russian, past tense verbs agree with the subject in gender and number. Since сотрудник is masculine singular, the verb must also be masculine singular:

• Сотрудник проверил люк.
• If the subject were feminine, for example сотрудница, it would be:
  • Сотрудница проверила люк.

Проверить is a perfective verb.

That matters because Russian verbs usually come in aspect pairs:

• проверять = imperfective
• проверить = perfective

In this sentence, проверил shows a completed action: the employee checked the hatch, and the action is viewed as finished.

Compare:

• Сотрудник проверил люк. = He checked it / completed the check.
• Сотрудник проверял люк. = He was checking it / he checked it repeatedly / the action is described as a process.

It is in a different case logically: it is the direct object, so it is in the accusative case.

But for masculine inanimate singular nouns, the accusative looks exactly the same as the nominative.

So:

• nominative: люк
• accusative: люк

That is why the form does not visibly change.

If it were a masculine animate noun, you would often see a difference. For example:

• nominative: сотрудник
• accusative: сотрудника
  if it were the object of a verb

Russian has no articles.

So Сотрудник проверил люк can mean things like:

• The employee checked the hatch
• An employee checked a hatch
• The employee checked a manhole
• etc.

Which one sounds best depends on context. Russian usually lets context do the job that a/an/the do in English.

Сотрудник usually means employee, worker, staff member, or sometimes associate/official, depending on context.

It is a fairly common and neutral word. It often refers to someone who works for an organization, company, office, department, and so on.

A few related forms:

• сотрудник = male employee / masculine form
• сотрудница = female employee
• сотрудники = employees

Люк usually means a hatch, trapdoor, access cover, or manhole cover/opening, depending on context.

It is a practical, physical object you open or inspect, such as:

• a roof hatch
• a maintenance hatch
• a manhole
• an access panel

So the exact English word can change based on the situation, even though the Russian word stays the same.

Сотрудник проверил люк uses the most neutral, basic word order: subject + verb + object.

That is often the clearest default order in Russian too.

But Russian word order is more flexible than English, because case endings help show grammatical roles. So you could also see:

• Люк проверил сотрудник.

This still means roughly the same thing, but the emphasis changes. It may sound like It was the hatch that the employee checked or place extra focus on люк.

So the original sentence is the most neutral version.

The stress is:

• сотру́дник
• прове́рил
• люк

A rough pronunciation guide:

• сотру́дник ≈ sa-TROOD-neek
• прове́рил ≈ pra-VYE-reel
• люк ≈ lyook

A few notes:

• ю in люк sounds like yu, but after л it gives a soft л sound: lyuk
• Unstressed o is usually pronounced closer to a in normal speech
• Russian stress is important because it is not always predictable

You could, but it is usually unnecessary here.

Russian often leaves out subject pronouns when the subject is already clear. Since сотрудник is explicitly stated, adding он would usually be redundant.

Natural:

• Сотрудник проверил люк.

Less necessary here:

• Он, сотрудник, проверил люк.

Russian does not need a separate word like he when the noun subject is already present.

You would probably use the imperfective verb instead of the perfective one.

So:

• Сотрудник проверял люк.

This can suggest:

• he was checking the hatch
• he checked the hatch for some time
• he checked it repeatedly
• the action is presented as a process, not as a single completed result

By contrast:

• Сотрудник проверил люк.

focuses on the fact that the check was completed.

Not naturally with сотрудник + проверил, because both forms are masculine.

For a female employee, Russian normally uses:

• Сотрудница проверила люк.

That changes both:

• the noun: сотрудник → сотрудница
• the verb: проверил → проверила

So the original sentence strongly points to a male employee, or at least uses masculine grammar.

Yes, that is a very good habit in Russian.

It is best to learn verbs in aspect pairs whenever possible:

• проверять = imperfective
• проверить = perfective

If you only memorize one form, it will be harder later to express:

• ongoing action
• repeated action
• completed action
• future meaning

For example:

• Я проверяю люк. = I am checking / I check the hatch.
• Я проверю люк. = I will check the hatch (perfective future).
• Я проверил люк. = I checked the hatch / finished checking it.

So yes: learning the pair is very useful.