Learn Hardcore Russian: Взрослый человек сам отвечает за своё здоровье. - An adult person is responsible for their own health.

взрослый человек literally means an adult person.
You can use взрослый as a noun on its own (meaning an adult), for example:
- Взрослые должны показывать хороший пример. – Adults should set a good example.

In this specific sentence, взрослый человек sounds a bit more neutral and complete, like stressing that we are talking about a person who is an adult, not a child. Using взрослый alone here would also be understandable, but it might sound more general or stylistically different.

What nuance does сам add in сам отвечает?

сам here emphasizes that the adult is personally / by himself or herself responsible.

отвечает за своё здоровье – is responsible for their health (a neutral fact).
сам отвечает за своё здоровье – is themself responsible for their own health, implying:
- No one else (parents, government, etc.) should be expected to take primary responsibility.
- The responsibility is not shared or shifted to someone else.

So сам adds the idea of self-responsibility / personal responsibility and light emphasis.

Can сам be left out? What changes?

Yes, you can say:

Взрослый человек отвечает за своё здоровье.

This still means that an adult is responsible for his or her health, but it is a bit more matter‑of‑fact, less emphatic.

With сам, the sentence underlines that it is specifically the adult, not anyone else, who should take responsibility. Without сам, it is more of a general rule stated less emotionally or less strongly.

What is the role of за in отвечает за своё здоровье?

The verb отвечать with the preposition за means to be responsible for something or someone.

отвечать за что? – to be responsible for what?
отвечать за кого? – to be responsible for whom?

So за here is required by this meaning of отвечать.

Do not confuse this with отвечать на:

отвечать на вопрос – to answer a question.

So:

отвечать за здоровье – to be responsible for health.
отвечать на вопрос – to answer a question.

Why is it своё здоровье and not его здоровье or её здоровье?

своё is the reflexive possessive pronoun. It refers back to the subject of the sentence:

Subject: взрослый человек
Possessor: the same взрослый человек
So we use своё здоровье – his/her own health.

If you say:

Взрослый человек отвечает за своё здоровье. – The adult is responsible for their own health.
Взрослый человек отвечает за его здоровье. – The adult is responsible for his health (some other man, not the adult themself).
Взрослый человек отвечает за её здоровье. – The adult is responsible for her health (some woman, not the adult themself).

So своё clearly shows that the health belongs to the subject of the sentence.

What are the different forms of свой, and why do we use своё here?

свой changes according to gender, number, and case of the noun it describes, just like other possessive adjectives (e.g. мой, твой).

Nominative singular forms:

свой – masculine
своя – feminine
своё – neuter
свои – plural

The noun здоровье is neuter in Russian, so in the accusative singular (with no visible ending change), the matching form is своё:

своё здоровье – one’s own health.

So we use своё because здоровье is neuter singular.

What case is своё здоровье, and why?

здоровье here is in the accusative case, and своё agrees with it (neuter accusative singular).

Reason: the prepositional construction отвечать за requires the accusative:

отвечать за что? – за работу, за детей, за здоровье (all accusative).

So:

за своё здоровье – for one’s own health (accusative object of за).

Why is it отвечает (imperfective, present tense) and not a different form like ответит?

отвечает is the imperfective present tense. Here it expresses a general truth / rule, not a one‑time event.

Взрослый человек сам отвечает за своё здоровье.
– An adult is (generally) responsible for their health; this is a standard principle.

If you use perfective ответит, you talk about a single future act, which would sound strange here:

Взрослый человек сам ответит за своё здоровье.
– Suggests: At some specific point in the future, the adult will be held accountable for their health.
This is much less like a general principle and more like a threat or prediction.

So the imperfective present (отвечает) is natural for a general statement.

Can we change the word order, for example: Взрослый человек отвечает за своё здоровье сам?

You can say:

Взрослый человек отвечает за своё здоровье сам.

This is grammatically correct. The meaning is still that the adult is personally responsible.

However, the original order:

Взрослый человек сам отвечает за своё здоровье.

sounds more natural and places earlier emphasis on сам (on who takes responsibility). When сам comes right after the subject, it strongly highlights that subject: Взрослый человек сам…

Putting сам at the end often sounds like afterthought emphasis or like a contrast (e.g. не врач, не родители, а он сам), but it is still acceptable.

Could we omit человек and just say Взрослый сам отвечает за своё здоровье?

Yes, you can say:

Взрослый сам отвечает за своё здоровье.

Here взрослый is used as a noun: an adult. The meaning stays the same.

Stylistically:

Взрослый человек сам отвечает… – a bit more neutral, explicit, maybe slightly more formal.
Взрослый сам отвечает… – a bit more compact and can sound more like a slogan or proverb.

Both are correct.

What is the difference between отвечать за здоровье and нести ответственность за здоровье?

Both can translate to be responsible for health, but there is a nuance:

отвечать за здоровье – very common, everyday; can be used in both informal and formal speech.
нести ответственность за здоровье – literally to bear responsibility for health; sounds more formal and bureaucratic, often in legal or official contexts.

In normal speech about personal responsibility, отвечать за своё здоровье is more natural and idiomatic.

How is взрослый different from words like большой or старший?

взрослый – adult, grown‑up, contrasted with child; focuses on legal / social adulthood.
большой – big, large, also sometimes grown‑up when speaking to children (e.g. ты уже большой – you are big now), but it is not the standard word for adult.
старший – older, elder, senior (comparative of старый). It compares ages or ranks, not the child/adult distinction by itself.

So in this sentence we specifically mean an adult, so взрослый человек is the correct and natural phrase.

How do we pronounce здоровье and where is the stress?

здоровье is pronounced roughly as zda-ROV-ye in English transcription.

Stress is on the second syllable: здоро́вье.
The final ье is a soft -ye sound.
The first consonant cluster зд is pronounced together, like zd in Lodz for English speakers who know Polish, or like z plus d run together.

So syllables: здо-РО-вье with stress on РО.