Op zaterdag lees ik thuis.

Because Dutch often puts a time expression at the beginning of the sentence.

In Dutch, the first position can be filled by different kinds of information:

• the subject: Ik lees thuis.
• the time: Op zaterdag lees ik thuis.
• the place: Thuis lees ik op zaterdag.

Starting with Op zaterdag gives extra emphasis to when it happens.

This is because of the Dutch verb-second rule.

In a main clause, the finite verb must be in the second position. If you begin with something other than the subject, the verb still stays second, and the subject comes after it.

So:

• Ik lees thuis.
• Op zaterdag lees ik thuis.

Structure:

• Op zaterdag = first position
• lees = second position, so the verb must come here
• ik = subject, now placed after the verb

This word order is very common in Dutch.

Usually op zaterdag means on Saturdays / on Saturday in a general, habitual sense.

So in this sentence, it normally means something like:

• I read at home on Saturdays
• On Saturday, I read at home

Dutch often uses the singular day name for repeated habits:

• op maandag = on Mondays
• op vrijdag = on Fridays
• op zaterdag = on Saturdays

If you really want to stress repetition, you might also hear:

• op zaterdagen

But op zaterdag is very normal for a routine.

Because in Dutch, days of the week usually appear without an article in expressions like this.

So you say:

• op maandag
• op dinsdag
• op zaterdag

Not:

• op de zaterdag in normal standard usage for this meaning

The form without an article is the usual way to express on Monday / on Saturday.

Dutch uses op with days of the week when meaning on a certain day.

So:

• op maandag = on Monday
• op zaterdag = on Saturday

English and Dutch match quite closely here:

• on Saturday → op zaterdag

You may sometimes hear a day name without op in informal contexts, but for learners, op + day is the safest and most standard pattern.

Lees is the present tense form of the verb lezen for ik.

Conjugation of lezen in the present tense:

• ik lees
• jij leest
• u leest
• hij/zij/het leest
• wij lezen
• jullie lezen
• zij lezen

So in this sentence:

• lees = read
• ik = I

Even though ik comes after the verb here, the verb form is still the one that belongs with ik.

This is a very common question.

• huis means house/home as a noun
• thuis means at home/home as an adverb

So:

• Ik ben thuis. = I am at home.
• Dit is mijn huis. = This is my house.

In your sentence, thuis is correct because it describes where the reading happens:

• Op zaterdag lees ik thuis. = On Saturdays I read at home.

You would not normally say ik lees huis.

Yes, absolutely.

Both are grammatical:

• Op zaterdag lees ik thuis.
• Ik lees op zaterdag thuis.

The difference is mainly focus:

• Op zaterdag lees ik thuis. emphasizes when
• Ik lees op zaterdag thuis. is more neutral and starts with the subject

Dutch word order is flexible, but the finite verb still has to stay in the correct place in a main clause.

In Dutch, days of the week are not capitalized unless they begin the sentence.

So:

• op zaterdag
• op maandag
• zondag is rustig

This is different from English, where Saturday and Monday are always capitalized.

Yes, it can.

For example:

• Op zaterdag lees ik thuis.
• Ik lees thuis op zaterdag.
• Thuis lees ik op zaterdag.

These versions can all be grammatical, but they sound slightly different in emphasis.

A useful learner rule is:

• time and place expressions can move around
• but in a main clause, the finite verb still stays in second position

So if you start with Thuis, you get:

• Thuis lees ik op zaterdag.

not:

• Thuis ik lees op zaterdag

Yes, it is completely natural.

It is a simple and correct Dutch main clause with:

• a time phrase first: Op zaterdag
• the finite verb second: lees
• the subject after the verb: ik
• a place adverb at the end: thuis

It is a very good example of basic Dutch word order.