Om lørdagen plejer min bror at lave mad hjemme, fordi restauranterne er dyre.

Om lørdagen means on Saturdays or on Saturday(s) as a regular habit.

By contrast, på lørdag usually means this Saturday / on Saturday as one specific day.

So:

• Om lørdagen = regularly, on Saturdays
• På lørdag = one particular Saturday

You can also compare hver lørdag, which means every Saturday. That is close in meaning, but om lørdagen is a very common and natural Danish way to talk about a repeated habit.

In Danish, expressions like om mandagen, om tirsdagen, om lørdagen are a common way to mean on Mondays / Tuesdays / Saturdays in a habitual sense.

So the definite form -en here is part of a standard time expression. It does not mean the Saturday in the same way English would use the. It is just how Danish often builds this kind of recurring-time phrase.

This is because Danish is a V2 language in main clauses. That means the finite verb usually comes in second position.

Here, the sentence begins with the time expression Om lørdagen. Since that first slot is already taken, the finite verb plejer must come next, and the subject min bror comes after it:

• Om lørdagen plejer min bror ...

If you start with the subject instead, the order becomes:

• Min bror plejer at lave mad hjemme om lørdagen.

Both are correct. The version in your sentence gives more emphasis to when it happens.

Plejer means usually, tends to, or is in the habit of.

So min bror plejer at lave mad hjemme means something like:

• my brother usually cooks at home
• my brother tends to cook at home

It describes a habit, not something happening right now.

A useful comparison:

• Min bror laver mad hjemme = my brother cooks/is cooking at home (depending on context)
• Min bror plejer at lave mad hjemme = my brother usually cooks at home

Also, the past form plejede at means used to:

• Min bror plejede at lave mad hjemme = my brother used to cook at home

Because pleje is normally followed by at + infinitive.

So the pattern is:

• plejer at lave
• plejer at spise
• plejer at gå

This is just the normal construction.

A useful contrast is with modal verbs like kan, vil, skal, which do not use at:

• han kan lave mad
• han vil lave mad

But:

• han plejer at lave mad

Yes, literally it is make food, but idiomatically it means cook.

So lave mad is one of the most common Danish ways to say to cook.

Examples:

• Jeg laver mad = I am cooking / I cook
• Han elsker at lave mad = He loves cooking

The verb lave is very broad and often means make or do, so in combinations like lave mad you should learn the whole phrase as a unit.

Because hjemme means at home, while hjem usually means homeward / to home.

So:

• han er hjemme = he is at home
• han laver mad hjemme = he cooks at home
• han går hjem = he goes home

In your sentence, there is no movement toward home. It is about location, so hjemme is the right word.

Because mad here is being used in a general, uncountable sense, like food in English.

So:

• lave mad = cook food / cook
• spise mad = eat food

If you make it definite, it becomes specific:

• lave maden = cook the food / prepare the meal

So in your sentence, mad is general, not a specific dish or meal already identified.

Restauranterne is the definite plural form, literally the restaurants.

In Danish, the definite form is often used where English might simply use a bare plural like restaurants, especially when the speaker means the restaurants relevant in the situation, such as the local ones or the ones people would normally choose from.

So here restauranterne er dyre can naturally mean something like:

• the restaurants are expensive
• or, in smoother English, simply restaurants are expensive

If you say restauranter er dyre, that is also possible, but it sounds more like a broad general statement about restaurants in general.

Because Danish adjectives change form depending on gender and number.

With restaurant, the forms are:

• en dyr restaurant = an expensive restaurant
• et dyrt sted = an expensive place
• dyre restauranter = expensive restaurants

Since restauranterne is plural, the adjective must be dyre.

So:

• restauranterne er dyre = the restaurants are expensive

Yes. That is also correct and very natural.

The difference is mainly one of focus:

• Om lørdagen plejer min bror at lave mad hjemme puts the time expression first, so it highlights when
• Min bror plejer at lave mad hjemme om lørdagen starts with the subject, so it feels a bit more neutral

Because Danish uses the V2 rule, moving om lørdagen to the front changes the word order after it, but not the basic meaning.