Проверьте соединение: подтяните гайку или замените прокладку.

Because they are imperative forms addressed to either:

• more than one person, or
• one person politely/formally

So проверьте means check!, подтяните means tighten/pull tighter!, and замените means replace! in a polite or plural command.

The less formal singular forms would be:

• проверь
• подтяни
• замени

In technical instructions, Russian often uses the polite/plural imperative even when speaking to a single reader.

Russian often uses the perfective imperative when the speaker wants a complete, one-time result.

Here, the instructions are about finishing specific actions:

• проверьте = check it completely
• подтяните = tighten it up
• замените = replace it

If the imperfective were used instead, it could sound more like:

• a repeated/habitual instruction
• a process-focused command
• a softer or more general directive in some contexts

So in a repair/manual context, the perfective is very natural because the goal is a completed result.

Because соединение is the direct object of проверьте, and for an inanimate neuter noun in the singular, the accusative form is the same as the nominative.

So:

• nominative: соединение
• accusative: соединение

That is why the form does not visibly change.

Because both are feminine singular nouns, and here they are also direct objects, so they go into the accusative case.

Their dictionary forms are:

• гайка → гайку
• прокладка → прокладку

This is a very common pattern for feminine nouns ending in -а:

• лампа → лампу
• труба → трубу
• гайка → гайку

In this context, подтянуть means something like tighten up or tighten a bit more.

It often suggests that something is already in place, but needs to be made tighter. That fits well with a nut:

• подтянуть гайку = tighten the nut / snug up the nut

By contrast, затянуть can also mean tighten, but it is often more general and can sound like tighten fully or fasten tightly. In practical usage, both verbs may appear in technical contexts, but подтянуть often carries the nuance of re-tightening or taking up looseness.

In everyday Russian, соединение can mean connection, joint, link, or junction depending on context.

In a mechanical or plumbing-type instruction like this, it usually refers to the connection point where parts are joined together. So it is not just an abstract connection; it is a physical joint or fitting that may be leaking or loose.

Not always. Прокладка is a context-dependent technical word. It can mean:

• gasket
• seal
• packing
• sometimes another kind of inserted layer or lining

In this sentence, because it appears with гайка and соединение, the most likely meaning is gasket or seal.

So the exact English word depends on the device or system being discussed.

The colon introduces a more specific instruction after a general one.

Structure:

• Проверьте соединение: = Check the connection:
• подтяните гайку или замените прокладку. = tighten the nut or replace the gasket.

So the colon works much like in English when you say:

• Check the connection: tighten the nut or replace the gasket.

It signals that what follows explains how to deal with the connection.

Yes. Russian normally does not need to state the subject pronoun when the verb ending already shows it.

So the sentence effectively means:

• (You) check the connection: tighten the nut or replace the gasket.

The imperative forms themselves tell you that the instruction is directed at you (singular formal or plural).

This is the most neutral and natural order for an instruction:

• verb + object
• подтяните гайку
• замените прокладку

Russian word order is flexible, so other orders are possible, but they would usually add emphasis or sound less neutral.

For example:

• гайку подтяните could emphasize the nut
• прокладку замените could emphasize the gasket

In manuals and instructions, the straightforward verb + object order is standard.

Russian has no articles. It does not have direct equivalents of a/an and the as regular grammar words.

So nouns like:

• соединение
• гайку
• прокладку

can mean a connection / the connection, a nut / the nut, a gasket / the gasket, depending on context.

The context of a technical instruction makes them feel definite in English, so translation often uses the:

• the connection
• the nut
• the gasket

You would use the singular informal imperative forms:

• Проверь соединение: подтяни гайку или замени прокладку.

That is grammatically correct, but in manuals, instructions, and customer-facing technical language, the -те forms are much more common because they sound more standard and polite.

The main stresses are:

• прове́рьте
• соедине́ние
• подтяни́те
• га́йку
• или́
• замени́те
• прокла́дку

Stress is very important in Russian because it is not always predictable, so it is worth learning these together with the words.