После душа сын надел пижаму, а я надела тёплый халат.

Because после requires the genitive case.

• Dictionary form: душ = shower
• Genitive singular: душа

So:

• после душа = after the shower / after showering

This душа is not the separate word meaning soul here; it is just the genitive form of душ.

Russian has no articles, so сын by itself can correspond to the son, a son, or son depending on context.

In this sentence, because the speaker then says а я..., the natural interpretation is:

• сын = my son

Russian also often leaves out possessive words like мой when they are obvious from context.

In the past tense, Russian verbs agree with the subject in gender and number.

• сын надел = masculine singular
• я надела = feminine singular

So the speaker is female here.

If the speaker were male, it would be:

• а я надел тёплый халат

Because надел / надела is perfective: it presents the action as completed.

That fits this sentence well: first the shower happened, then the son put on pajamas, and the speaker put on a robe.

By contrast:

• надевал / надевала is imperfective
• it can mean was putting on, used to put on, or focus on the process rather than the completed result

So in a simple sequence of finished actions, надел / надела is the natural choice.

This is a classic Russian learner question.

• надеть = to put on a piece of clothing
• одеть = to dress a person

So:

• надеть пижаму
• надеть халат

But:

• одеть сына = to dress the son

A common mnemonic is:

• надеть одежду, одеть Надежду

In this sentence, the object is the clothing, so надеть is correct.

Yes, but the meaning shifts a little.

• сын оделся = the son got dressed
• сын надел пижаму = the son put on pajamas

So оделся is more general, while надел пижаму names the specific thing he put on.

If you want to mention the clothing, надел пижаму is very natural.

Because Russian treats пижама as a singular noun.

• пижама = pajamas / pyjamas
• Accusative singular: пижаму

So:

• сын надел пижаму = literally the son put on a pajama, but naturally it means put on pajamas

This is just a difference between how English and Russian package the idea.

They are the direct objects of надел / надела, so they go in the accusative case.

• пижама → пижаму
  feminine singular accusative
• халат → халат
  masculine singular inanimate accusative

For many masculine inanimate nouns, the accusative looks the same as the nominative, which is why халат does not change.

The adjective has to agree with халат in gender, number, and case.

• халат is masculine singular
• here it is accusative, but because it is inanimate, masculine accusative looks like nominative
• so the adjective also stays in the form тёплый

That is why you get:

• тёплый халат

Compare with a feminine noun:

• тёплая пижама
• надела тёплую пижаму

Here а links two parallel facts and adds a mild contrast or comparison:

• the son did one thing, and I did another

So in this sentence, а is often best understood as:

• and, but with a slight meanwhile / whereas / as for me feeling

It is not as strong as но (but), which usually signals a clearer contradiction.

So:

• ..., а я надела тёплый халат
  feels like ..., and I, for my part, put on a warm robe

No, Russian word order is fairly flexible.

This version:

• После душа сын надел пижаму, а я надела тёплый халат

puts После душа first to set the time frame: after the shower.

You could also say:

• Сын после душа надел пижаму...

That is also grammatical, but the emphasis is a little different. The original sentence sounds natural because it starts by establishing when everything happened.

Ё is pronounced yo.

So:

• тёплый sounds roughly like TYOP-lyi

A useful fact: ё is always stressed.

In many everyday Russian texts, people write е instead of ё, so you may often see:

• теплый

But the intended pronunciation is still тёплый. In learner materials, children’s books, dictionaries, and places where clarity matters, ё is more often written explicitly.