Циркуляция слабая.

In Russian, the verb to be is usually omitted in the present tense.

So:

• Циркуляция слабая = The circulation is weak

Russian does this very often:

• Он врач = He is a doctor
• Комната маленькая = The room is small
• Погода хорошая = The weather is good

If you want past or future, then a form of быть appears:

• Циркуляция была слабая = The circulation was weak
• Циркуляция будет слабая = The circulation will be weak

Because циркуляция is a feminine noun, and adjectives must agree with the noun in gender, number, and case.

Here the noun is:

• циркуляция — feminine, singular, nominative

So the adjective must match:

• masculine: слабый
• feminine: слабая
• neuter: слабое
• plural: слабые

Compare:

• Пульс слабый = The pulse is weak
• Циркуляция слабая = The circulation is weak
• Давление слабое = The pressure is weak/low depending on context
• Мышцы слабые = The muscles are weak

It is in the nominative case.

This sentence is basically a simple statement of the form:

• X is Y

In present-tense Russian sentences like this, the subject is normally in the nominative:

• циркуляция = the subject
• слабая = the predicate adjective describing it

So:

• Циркуляция = nominative singular feminine
• слабая = nominative singular feminine, matching it

Because here слабая is part of the predicate: it is saying something about the circulation.

• Циркуляция слабая = The circulation is weak

If you put the adjective before the noun, you get a noun phrase, not a complete sentence:

• слабая циркуляция = weak circulation

So the difference is:

• слабая циркуляция = just a phrase
• Циркуляция слабая = a full statement

Russian often uses this pattern:

• Погода хорошая
• Идея интересная
• Память плохая

Yes, but it usually means something slightly different in structure.

• Слабая циркуляция is mainly a phrase: weak circulation
• Циркуляция слабая is a sentence: The circulation is weak

Depending on context, Слабая циркуляция could also work as a sentence fragment, especially in notes, headlines, or medical comments. But as a clear full sentence for a learner, Циркуляция слабая is the more obvious subject + description pattern.

Russian has both full adjective forms and short adjective forms.

For weak, the feminine forms are:

• full form: слабая
• short form: слаба

So you may see:

• Циркуляция слабая
• Циркуляция слаба

Both can mean The circulation is weak, but they do not feel exactly the same.

Very roughly:

• слабая sounds more natural in everyday speech and common description
• слаба can sound more formal, literary, or concise

For many learners, Циркуляция слабая is the easier and more common pattern to start with.

A helpful approximation is:

• циркуляция → tseer-koo-LYA-tsee-ya
• слабая → SLA-ba-ya

Stress:

• циркуля́ция
• сла́бая

A more connected pronunciation guide:

• tseer-koo-LYA-tsee-ya SLA-ba-ya

A few sound notes:

• ц sounds like ts
• я after a consonant often adds a ya sound
• unstressed vowels are reduced in real speech, so native pronunciation may sound a bit less like the spelling suggests

No. Циркуляция is a general word meaning circulation.

It can refer to things like:

• blood circulation
• air circulation
• water circulation
• circulation of information
• other kinds of movement in a system

So the sentence Циркуляция слабая depends on context. In a medical context, it may suggest poor circulation in the body. In another context, it could refer to air or fluid flow.

Yes, it is natural, especially in contexts where someone is making a brief assessment.

For example:

• a doctor commenting on a patient
• someone discussing air flow in a room
• a short written note
• a concise spoken observation

Russian often prefers short, direct statements like this.

That said, in a specific medical context, native speakers might also use more specific wording, such as:

• Кровообращение слабое = The blood circulation is weak / poor
• Плохая циркуляция крови = Poor blood circulation

But Циркуляция слабая is still correct and natural.

The dictionary forms are:

• циркуляция = circulation
• слабый = weak

In the sentence, слабый changes form to match циркуляция:

• dictionary form: слабый
• used here: слабая

This is very common in Russian, so it is worth learning adjectives by their dictionary masculine form, while getting used to how they change:

• слабый
• слабая
• слабое
• слабые

Often, yes.

Depending on context, English may prefer:

• The circulation is weak
• The circulation is poor

Both can work. Russian слабая literally means weak, but natural English sometimes uses poor where Russian uses weak.

So if the meaning has already been given to you, just remember that Russian and English do not always choose the exact same adjective in real-life usage.