У неділю я вдома.

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

So:

• Я вдома. = I am at home.
• literally: I at home

This is completely normal in Ukrainian.
If you want to talk about the past or future, forms of бути appear:

• Я був / була вдома. = I was at home.
• Я буду вдома. = I will be at home.

So in У неділю я вдома, the idea of am is understood automatically.

Because after у / в meaning on with days of the week, Ukrainian uses the accusative case.

The dictionary form is:

• неділя = Sunday

But in this sentence it becomes:

• у неділю = on Sunday

This pattern is very common:

• у понеділок = on Monday
• у вівторок = on Tuesday
• у середу = on Wednesday
• у неділю = on Sunday

So неділя changes to неділю because of the grammar after у.

It is the accusative singular of неділя.

Here is the basic change:

• неділя → nominative
• неділю → accusative

For many feminine nouns ending in -я, the accusative singular ends in -ю.

So:

• неділя → неділю
• земля → землю
• сім’я → сім’ю

In у неділю, the accusative is used because the phrase means on Sunday.

Both у and в can mean in / at / on in many contexts. Ukrainian often chooses between them for easier pronunciation and smoother sound.

So:

• у неділю
• в неділю

Both are possible, and both mean the same thing here.

Speakers often prefer one or the other depending on the sounds around it. Since неділю starts with н, у неділю sounds very natural.

This is a feature of Ukrainian called euphony: choosing forms that sound smoother.

Вдома means at home or home, depending on the English sentence.

Examples:

• Я вдома. = I am at home.
• Вона вдома. = She is home / at home.

A useful thing to know: вдома is an adverb, not a noun phrase like English at home.

That means it does not change for case, gender, or number.

Because вдома is the normal fixed adverb meaning at home.

Compare:

• вдома = at home
• в домі = in the house

These are not exactly the same.

Вдома focuses on the idea of being at home as a state or location connected with one’s home life.
В домі is more literally in the house/building.

So in a simple sentence like I’m at home, Ukrainian normally says:

• Я вдома.

You may hear дома in everyday speech, especially under Russian influence or in colloquial usage, but вдома is the standard Ukrainian form.

So for learners, the best choice is:

• Я вдома.

That is the safest and most natural standard Ukrainian version.

Yes, Ukrainian word order is more flexible than English word order.

У неділю я вдома is a natural neutral way to say:

• On Sunday, I’m at home.

Other possible orders include:

• Я вдома у неділю.
• Я у неділю вдома.
• Вдома я у неділю. — more marked, depending on emphasis

The sentence-initial У неділю puts the time first, like setting the scene: As for Sunday...

So the original order is very natural if you want to emphasize when.

Yes, it can mean either one, depending on context.

It may mean:

• on Sunday in a general statement
• this Sunday if the conversation is about the coming week
• sometimes even on Sundays in a habitual sense, though often Ukrainian would use other wording to make habitual meaning clearer

Examples:

• У неділю я вдома. = I’m at home on Sunday / this Sunday.
• Щонеділі я вдома. = I’m at home every Sunday.

So context tells you whether it is one specific Sunday or a more general idea.

In this sentence, я is usually kept.

Because there is no present-tense verb like am, the pronoun helps make the subject clear:

• У неділю я вдома. = On Sunday, I’m at home.

If you removed я:

• У неділю вдома.

that would sound incomplete by itself in many situations, unless the subject is already very obvious from context.

So for learners, it is best to include я here.

A helpful pronunciation guide is:

• У неділю я вдома
• roughly: u ne-DI-lyu ya vDO-ma

Stress:

• неділю → stress on ді
• вдома → stress on до

A few notes:

• я sounds like ya
• ю in неділю sounds roughly like yu
• вдома begins with a consonant cluster вд-, which may feel unusual at first; listen and repeat slowly: в-до-ма

It is an adverb.

That is important because adverbs do not agree with the subject and do not change form like adjectives do.

So:

• Я вдома. = I am at home.
• Він вдома. = He is at home.
• Вони вдома. = They are at home.

The word вдома stays the same in all of these.

Usually the most direct meaning is simply:

• On Sunday, I am at home.

Depending on context, English might phrase it as:

• I’m home on Sunday.
• I stay home on Sunday.

But the Ukrainian sentence itself does not contain a separate verb meaning stay. It just states location/state: I am at home.

If you specifically want I stay home on Sunday, Ukrainian might use a verb such as:

• У неділю я залишаюся вдома.

So У неділю я вдома is simpler and more neutral.