La domenica faccio colazione con la mia famiglia.

Because la domenica usually means on Sundays / every Sunday as a habit.

In Italian, the definite article before a day of the week often gives it a habitual, repeated meaning:

• La domenica faccio colazione con la mia famiglia = I do this regularly on Sundays
• Domenica faccio colazione con la mia famiglia = this Sunday / on Sunday

So the article la is important here because it helps show that this is a routine.

Italian usually does not use a preposition before days of the week the way English uses on.

So:

• domenica = on Sunday
• la domenica = on Sundays / every Sunday

This is very normal in Italian. English needs on, but Italian often just uses the day itself, with or without the article depending on the meaning.

In this sentence, it means all Sundays in general or every Sunday.

That is one of the most useful things to remember:

• domenica = Sunday / this Sunday
• la domenica = on Sundays, as a habit

Italian also has other ways to express the same idea, such as:

• ogni domenica = every Sunday
• di domenica = on Sundays

But la domenica is very common and natural.

Yes, faccio comes from fare, which often means to do or to make. But in Italian, fare colazione is a fixed expression meaning to have breakfast or to eat breakfast.

So even though the literal word-for-word idea looks like I make breakfast, that is not how it functions here. It is simply the normal Italian way to say I have breakfast.

This is a good example of how Italian and English often use different verbs in everyday expressions.

Because fare colazione is a fixed idiomatic expression, and in that expression colazione normally appears without an article.

So you say:

• faccio colazione = I have breakfast

not normally:

• faccio la colazione

If you add an article, the meaning or structure usually changes. For example:

• faccio una buona colazione = I have a good breakfast
• preparo la colazione = I prepare the breakfast

So in the basic expression fare colazione, no article is the normal choice.

Faccio is the first person singular present indicative of fare.

So it means I do / I make, or in this expression, I have breakfast.

The present tense here is used for a habitual action, just like in English:

• La domenica faccio colazione... = On Sundays I have breakfast...

Also, fare is an irregular verb, so faccio is not built in a completely regular way.

A few present-tense forms are:

• io faccio
• tu fai
• lui/lei fa
• noi facciamo
• voi fate
• loro fanno

Because in Italian, possessive adjectives usually go with a definite article:

• la mia famiglia = my family
• il mio libro = my book
• i miei amici = my friends

So la mia famiglia is the normal form.

English does not use an article in this kind of phrase, but Italian usually does.

That is true for many singular immediate family members, but famiglia is not part of that common exception.

For example, Italian often says:

• mia madre
• mio padre
• mio fratello

without the article.

But with famiglia, the article is normally kept:

• la mia famiglia

So this sentence follows the standard rule.

Yes. That is completely correct and very natural.

• La domenica faccio colazione con la mia famiglia
• Ogni domenica faccio colazione con la mia famiglia

Both mean essentially the same thing.

A small difference in feel:

• la domenica sounds like a general weekly routine
• ogni domenica sounds a little more explicit, like every single Sunday

In most situations, either one works.

Yes. Italian word order is more flexible than English word order.

The original sentence is very natural:

• La domenica faccio colazione con la mia famiglia

It starts with the time expression, which sets the scene clearly.

You could also say:

• Faccio colazione con la mia famiglia la domenica

That is still understandable and correct, but the original version sounds a bit more neutral and natural as a statement about routine.

So the sentence order used here is a very common and good one to learn.

Two things signal that:

• la domenica = on Sundays, habitually
• the present tense in Italian often expresses regular actions

So the sentence is understood as a routine:

• On Sundays, I have breakfast with my family

Italian uses the present tense for habitual actions very naturally, just like English does in sentences such as I have breakfast with my family on Sundays.