Он положил руку на грудь.

Положил is the past tense, masculine singular form of положить.

Why it looks this way:

• положить = dictionary form / infinitive
• положил = he put / placed
• Russian past tense agrees with the subject in gender and number

So:

• он положил = he put
• она положила = she put
• оно положило = it put
• они положили = they put

Because the subject here is он, the verb has to be положил.

Because рука is the direct object of the verb, so it goes into the accusative case.

• Nominative: рука = hand
• Accusative singular: руку = hand

In this sentence, the person is doing something to the hand as an object of the action: he placed a/the hand somewhere.

A useful pattern:

• вижу руку = I see a/the hand
• поднял руку = raised a/the hand
• положил руку = placed a/the hand

So руку is exactly what you would expect after a transitive verb like положить.

Because на can take different cases depending on the meaning.

Here the idea is motion toward a surface / onto something, so Russian uses the accusative:

• на грудь = onto the chest

Compare:

• Он положил руку на грудь. = He put his hand onto his chest.
  → movement to a destination → accusative
• Рука лежит на груди. = The hand is lying on the chest.
  → location, no movement → prepositional

So:

• на + accusative = motion onto / to
• на + prepositional = location on

Russian often omits possessive words like his, her, or my when the ownership is obvious, especially with body parts.

So:

• Он положил руку на грудь. naturally means He put his hand on his chest.

Russian does this because the subject already makes the meaning clear. In many contexts, adding a possessive would sound unnecessary.

You could say:

• Он положил свою руку на грудь.

But that is usually more emphatic, contrastive, or stylistically heavier, something like:

• He put his own hand on his chest

So the version without свою is the normal, natural one.

This is an aspect question.

• положить = perfective
• класть = imperfective

In this sentence, положил shows a completed action: he put his hand on his chest, and the action is treated as a whole.

Compare:

• Он положил руку на грудь. = He put his hand on his chest.
  → one completed act
• Он клал руку на грудь. = He was putting / used to put his hand on his chest.
  → process, repetition, or background action

For a single completed event, положил is the normal choice.

In this sentence, грудь is best understood as chest.

The noun грудь can refer to the front upper part of the torso in general. Depending on context, English may translate it as:

• chest
• sometimes breast

But in a sentence like Он положил руку на грудь, the natural English meaning is He put his hand on his chest.

So although the Russian word can cover slightly different meanings depending on context, here chest is the safest and most natural interpretation.

Yes. Nouns ending in -ь can be either masculine or feminine, so you have to learn the gender of each one.

Грудь is feminine.

That matters for adjectives and pronouns:

• левая грудь = left breast/chest side
• моя грудь = my chest

Some forms:

• nominative: грудь
• accusative: грудь
• prepositional: на груди
• genitive: груди

So even though the ending may look unusual to an English speaker, it is a normal feminine noun.

Because for this noun, the accusative singular has the same form as the nominative singular.

So:

• nominative: грудь
• accusative: грудь

This happens with many feminine nouns, especially some that end in -ь.

That is why the phrase is:

• на грудь
  not because nothing is happening grammatically, but because the accusative form just happens to look the same as the base form.

Yes. Russian word order is more flexible than English word order because the case endings show the grammatical roles.

The neutral order here is:

• Он положил руку на грудь.

But other orders are possible, for example:

• Руку он положил на грудь.
• На грудь он положил руку.

These versions may sound more emphatic or focus attention on a particular part of the sentence.

Very roughly:

• Он положил руку на грудь. = neutral statement
• Руку он положил на грудь. = emphasizes the hand
• На грудь он положил руку. = emphasizes onto the chest

So yes, the order can change, but the neutral learner-friendly version is the one given.

A natural stress pattern is:

• Он положи́л ру́ку на грудь.

Key stresses:

• положи́л
• ру́ку

A few pronunciation notes:

• он sounds roughly like on
• положил has stress on the last syllable: па-ла-ЖИЛ (approximately)
• руку has stress on the first syllable: РУ-ку
• грудь is one syllable, ending in a soft consonant

The final дь in грудь is soft, which may take practice for English speakers.

They are:

• он = he
• положить = to put, place
• рука = hand, arm
• грудь = chest, breast

In the sentence, some of them appear in changed forms:

• положил ← from положить
• руку ← from рука
• грудь stays грудь, but here it is functioning as the accusative after на with motion

This is a very normal pattern in Russian: the dictionary form changes depending on grammar.