Двигатель работает тихо.

Двигатель means engine or motor, depending on context.

Here it is in the nominative singular, because it is the subject of the sentence — the thing doing the action.

• двигатель = engine
• subject of работает = двигатель

Russian often has no articles, so двигатель could mean:

• the engine
• an engine

You figure that out from context.

Работает is the 3rd person singular form of работать (to work, to operate, to function).

It matches двигатель, which is singular:

• я работаю = I work
• ты работаешь = you work
• он / она / двигатель работает = he / she / it / the engine works

So двигатель работает literally means the engine works / is operating / is running.

It can mean either, depending on context.

With machines, работать often means:

• to work in the sense of to function
• to run in the sense of to be operating

So Двигатель работает тихо can naturally correspond to:

• The engine works quietly
• The engine is running quietly
• The engine operates quietly

In English, is running quietly is often the most natural translation for an engine.

Because тихо is being used as an adverb, meaning quietly.

Compare:

• тихий двигатель = a quiet engine
  (тихий is an adjective describing the noun)
• двигатель работает тихо = the engine runs quietly
  (тихо is an adverb describing how it runs)

So here тихо describes the manner of the action, not the noun itself.

It can be more than one thing.

In this sentence, тихо is best understood as an adverb: quietly.

But forms like тихо can also be used in predicative expressions, for example:

• Здесь тихо. = It is quiet here.

So you will often see тихо translated as either:

• quietly when it modifies a verb
• quiet when it describes the overall situation

In Двигатель работает тихо, it modifies работает, so quietly is the best explanation.

Yes. Russian word order is fairly flexible.

The neutral order here is:

• Двигатель работает тихо.

But you could also hear:

• Тихо работает двигатель.
• Работает двигатель тихо.

These versions usually shift emphasis rather than basic meaning.

For example:

• Двигатель работает тихо. = neutral statement
• Тихо работает двигатель. = emphasis on quietly
• Работает двигатель тихо. = possible in context, often contrastive

For learners, the original order is the best default.

Russian does not have articles like English the and a/an.

So двигатель by itself can mean:

• the engine
• an engine

Context tells you which one is meant.

This is completely normal in Russian. You do not need to add anything.

A helpful pronunciation guide is:

DVEE-ga-tyel ra-BO-ta-yet TEE-kə

More carefully:

• двигатель → stress on the first syllable: двИгатель
• работает → stress on бо: рабОтает
• тихо → stress on the first syllable: тИхо

A rougher English-style approximation:

• DVEE-guh-tyel
• ruh-BOH-tuh-yet
• TEE-khuh

A few notes:

• г is like g in go
• х is like the ch in Scottish loch or German Bach
• unstressed o is often pronounced closer to a in normal speech

Russian usually prefers the actual noun when introducing or identifying the subject.

So instead of saying it, Russian often says:

• Двигатель работает тихо. = The engine runs quietly.

You can use pronouns in Russian, but they are often omitted unless needed for clarity or emphasis. Since двигатель is already named, there is no need for он here.

Работать is very common and natural for machines, devices, and systems.

Examples:

• Мотор работает. = The motor is running.
• Телефон не работает. = The phone doesn’t work.
• Компьютер работает медленно. = The computer works slowly.

For engines specifically, Russian can also use other verbs depending on nuance, but работает is one of the most basic and useful choices.

Not exactly.

• Двигатель тихий. = The engine is quiet.
  This describes a quality of the engine.
• Двигатель работает тихо. = The engine runs quietly.
  This describes how the engine is operating.

In many situations the meaning is similar, but the grammar and focus are different:

• тихий = adjective
• тихо = adverb

It can do both, just like English works.

Depending on context, it can mean:

• The engine is running quietly right now
• The engine runs quietly in general
• This engine operates quietly as a characteristic

Russian present tense often covers both current action and general truth/habitual action.

The straightforward negative is:

Двигатель не работает тихо.

This means:

• The engine does not run quietly.

If you want to say the engine is not working at all, then the meaning changes:

Двигатель не работает.

That means:

• The engine is not working
• The engine isn’t running

So be careful:

• не работает тихо = not quietly
• не работает = not functioning / not running