Мозок працює швидко.

• Мозок = brain
  It is the subject of the sentence.
• працює = works / is working / functions
  It is the verb.
• швидко = quickly / fast
  It is an adverb, describing how the brain works.

So the structure is:

subject + verb + adverb

Мозок is in the nominative singular form because it is the subject of the sentence.

In Ukrainian, the subject of a basic sentence usually appears in the nominative case.

Here:

• мозок = nominative singular
• masculine noun
• inanimate

If the word had a different role in the sentence, its form might change. For example, after some prepositions or as a direct object in certain contexts, you might see another case form.

Працює is the 3rd person singular present tense form of працювати (to work).

It matches the subject мозок, which is:

• third person (he/she/it type grammar)
• singular

So:

• я працюю = I work
• ти працюєш = you work
• він / вона / воно працює = he / she / it works
• мозок працює = the brain works

Because мозок is singular, the verb is singular too.

It can mean both, depending on context.

Ukrainian present tense often covers both:

• works
• is working

So Мозок працює швидко could be understood as:

• The brain works quickly
• The brain is working quickly
• sometimes even The brain functions quickly

English chooses between works and is working more explicitly than Ukrainian does.

Because the sentence needs an adverb, not an adjective.

• швидкий = fast, quick (adjective)
• швидко = quickly, fast (adverb)

In this sentence, the word describes the verb працює, not the noun мозок.

So:

• швидкий мозок = a fast/quick brain
• мозок працює швидко = the brain works quickly

That -о ending is very common for adverbs in Ukrainian.

Yes. In natural English, adverbs are often translated as either quickly or fast, depending on style.

So Мозок працює швидко may be translated as:

• The brain works quickly
• The brain works fast

Both are fine in English.

No, Ukrainian word order is more flexible than English word order.

The neutral order here is:

Мозок працює швидко.

But other orders are possible, for example:

• Швидко працює мозок.
• Мозок швидко працює.

These versions can shift emphasis slightly:

• putting швидко earlier can emphasize quickly
• putting мозок later can make it more contrastive or expressive

Still, for learners, Мозок працює швидко is the safest and most neutral order.

Because Ukrainian has no articles like English a / an / the.

So мозок can mean:

• a brain
• the brain

The exact meaning depends on context.

In this sentence, English would usually say the brain, but Ukrainian simply says мозок.

This is very normal:

• Книга на столі. = The book is on the table / A book is on the table
• Мозок працює швидко. = The brain works quickly

Context tells you which article sounds best in English.

A simple learner-friendly pronunciation guide is:

MO-zok prat-SYU-ye SHVYD-ko

Stress:

• мОзок
• працЮє
• швИдко

A few pronunciation notes:

• ц sounds like ts
• ю in працює gives a syu / tsyu-type sound
• шв at the start of швидко can feel a bit heavy for English speakers, but just practice it slowly: shv-

If you want to say it naturally, keep the rhythm smooth: МОзок працЮє швИдко.

Sometimes yes, but only if the subject is already clear from context.

Ukrainian often allows the subject to be omitted when it is understood. However, in a standalone sentence like this, мозок is useful because it tells you exactly what is working.

So:

• Мозок працює швидко. = clear, complete sentence
• Працює швидко. = Works quickly / Is working quickly, but now the listener has to guess what works quickly

For beginners, it is better to keep the subject in place unless context clearly supplies it.

Yes, працює is a normal and natural choice. It can mean:

• works
• is working
• functions

For body parts, machines, systems, and institutions, працювати is very common when you mean to function / to operate.

So Мозок працює швидко sounds natural.

Depending on context, Ukrainian could also use other verbs, but they would change the nuance:

• функціонує = functions
  More formal or technical.
• думає = thinks
  Not the same meaning.

So if you mean the brain is functioning/working quickly, працює is a good everyday choice.

The plural subject would be мозки (brains), and the verb would also change to plural:

• Мозки працюють швидко. = Brains work quickly.

Compare:

• singular: мозок працює
• plural: мозки працюють

This is a good example of subject-verb agreement in Ukrainian.

It is basically neutral.

Nothing in Мозок працює швидко is especially slangy, poetic, or highly formal. It would fit well in:

• ordinary explanation
• study materials
• general conversation
• simple scientific or educational context

If you wanted something more technical, you might choose a more specialized verb or add scientific vocabulary, but this sentence itself is plain and natural Ukrainian.