Моя жена сама приготовила ужин.

Because моя has to agree with жена in gender, number, and case.

• жена is feminine
• singular
• nominative here, because it is the subject

So the correct form is моя.

Compare:

• мой муж = my husband
• моя жена = my wife
• моё письмо = my letter
• мои друзья = my friends

Because жена is the subject of the sentence — the person doing the action.

In Моя жена сама приготовила ужин, the wife is the one who prepared the dinner, so жена stays in the nominative.

A very common rule in Russian is:

• subject → usually nominative
• direct object → often accusative

So here:

• моя жена = subject
• ужин = direct object

сама is the feminine form of сам, which adds emphasis. In this sentence it usually means something like:

• herself
• on her own
• personally

So it suggests that the wife prepared dinner herself, rather than someone else doing it for her.

Depending on context, сама can imply slightly different things:

• without help
• personally
• not someone else

So the nuance is stronger than just the basic verb.

Because сама agrees with жена, which is feminine singular.

The forms are:

• сам = masculine
• сама = feminine
• само = neuter
• сами = plural

Since the subject is жена, the correct form is сама.

Because it is referring back to the subject and agrees with it.

Here, сама is not a separate object like herself in English can sometimes feel like. It is more like an emphatic word attached to the subject:

• Моя жена сама... = My wife herself...

Since моя жена is nominative, сама is nominative too.

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

For singular past tense:

• masculine: usually -л
• feminine: usually -ла
• neuter: usually -ло
• plural: usually -ли

Since жена is feminine, the verb is приготовила.

Compare:

• Муж приготовил ужин.
• Жена приготовила ужин.
• Они приготовили ужин.

This is a question of aspect, which is very important in Russian.

• готовить / готовила = imperfective
• приготовить / приготовила = perfective

Here приготовила is perfective, which shows the action as completed: the dinner got prepared.

That is why it fits well for a finished result.

By contrast, готовила would usually focus more on the process, repeated action, or background action, for example:

• Она готовила ужин, когда я пришёл.
  She was cooking dinner when I arrived.

So in this sentence, приготовила is the natural choice because the action is presented as a completed whole.

Yes — ужин is in the accusative here. It just happens to look the same as the nominative.

That is normal for many masculine inanimate nouns in Russian:

• nominative: ужин
• accusative: ужин

So the case is different in function, but the form does not change.

Compare with a feminine noun, where the change is more visible:

• книга → книгу

No, Russian word order is much more flexible than English word order.

Моя жена сама приготовила ужин is a natural sentence, but other orders are also possible depending on emphasis.

For example:

• Моя жена сама приготовила ужин
  neutral, with emphasis on сама
• Моя жена приготовила ужин сама
  also natural; сама is emphasized a bit later
• Ужин моя жена приготовила сама
  stronger focus on ужин

So the words can move around, but the emphasis changes.

Yes, often it can be, if the context already makes it clear whose wife is being talked about.

For example:

• Жена сама приготовила ужин.

This can sound perfectly natural in conversation if the speaker’s wife is already understood.

However, моя жена is more explicit and is often the better form for learners, especially when the context is not obvious.

No. Russian has no articles like a or the.

So Russian simply says:

• жена
• ужин

and the listener figures out from context whether you mean something definite or indefinite.

That is why a full Russian sentence can look shorter than its English equivalent in this respect.