To je ta kniha, co chci číst.

To je is a very common Czech way to say this is / that is / it is.

In this sentence, to does not mean a specific it in the English sense. It often works more like a general pointing word: that, this, or it depending on context.

So To je ta kniha... is a natural way to introduce or identify something:

• To je Petr. = This/That is Petr.
• To je moje auto. = This/That is my car.

Here it is basically identifying the book.

Ta is the feminine singular form of ten, which often works like the/that.

Because kniha is:

• feminine
• singular
• in the nominative

the correct form is ta.

So:

• ten = masculine
• ta = feminine
• to = neuter

Since kniha is feminine, you say ta kniha.

In this sentence, ta kniha suggests a specific book, something like:

• that book
• the book

It helps show that we are talking about a particular book, not just any book.

Both co and která can introduce a relative clause like that / which / who in English.

So these are both possible:

• To je ta kniha, co chci číst.
• To je ta kniha, kterou chci číst.

The difference is mainly in style and grammar:

• co is very common in everyday spoken Czech.
• kterou is more formal and more grammatically explicit.

A learner should know this important point:

• co does not change form for case.
• který does change form, and here it would be kterou because it stands for knihu, the object of číst.

So co is easier and very common in conversation, while kterou is often preferred in more careful or formal Czech.

Because in the relative clause, the word referring back to kniha is the object of číst.

You want to read the book, so in the clause it functions like:

• chci číst knihu

The noun knihu is in the accusative.

When you replace knihu with a relative pronoun, you need the accusative feminine singular form of který, which is kterou:

• To je ta kniha, kterou chci číst.

So:

• která = nominative feminine singular
• kterou = accusative feminine singular

Czech often leaves out subject pronouns when they are clear from the verb form.

Chci already means I want, so já is not necessary.

Compare:

• chci = I want
• chceš = you want
• chce = he/she/it wants

Because the ending tells you the subject, Czech usually omits pronouns unless you want emphasis or contrast.

So:

• co chci číst = that I want to read

You could say co já chci číst, but that would sound more emphatic, like that I want to read.

Because after chtít (to want), Czech normally uses an infinitive, just like English does after want.

So:

• chci číst = I want to read
• chci spát = I want to sleep
• chci jít = I want to go

Here:

• chci = I want
• číst = to read

So the structure is very similar to English.

Kniha is in the nominative singular.

That is because in the main clause, ta kniha is the noun phrase being identified:

• To je ta kniha...

The sentence structure is like That is the book..., where ta kniha is the naming or identifying part.

Inside the relative clause, however, the book is understood as the object of číst:

• chci číst [tu knihu]

That object is not repeated when you use co, but it is still understood.

So there are really two layers:

1. ta kniha in the main clause: nominative
2. understood role in the relative clause: accusative object of číst

It is mostly neutral everyday Czech, with a slightly spoken feel because of co.

• To je ta kniha, co chci číst.
  Very natural in conversation.
• To je ta kniha, kterou chci číst.
  More formal or more carefully written.

A native speaker would definitely use the version with co in normal speech. So this is a good sentence to learn for real-life Czech.

Yes, you can, but the meaning changes slightly.

• To je ta kniha, co chci číst.
  = That is the book I want to read
  This points to a specific, identifiable book.

• To je kniha, co chci číst.
  = That is a book I want to read / That is the kind of book I want to read
  This can sound less specific.

In many contexts, ta helps make the sentence feel more definite and natural, especially if you mean one particular book.

Yes, Czech word order is flexible, but not every version sounds equally natural in every context.

The given sentence:

• To je ta kniha, co chci číst.

is very natural.

You may also hear:

• To je ta kniha, kterou chci číst.

If you move things around, the emphasis changes. For example:

• Tu knihu chci číst. = That book is the one I want to read.

But for the exact idea of identifying the book, the original word order is the most straightforward and natural.

Číst is pronounced roughly like cheest:

• č sounds like ch in chocolate
• í is a long ee
• st as written

So: číst ≈ cheest

The accent mark on í shows vowel length. In Czech, vowel length matters, so i and í are different sounds.

That is why it is important not to shorten it too much when speaking.

In everyday spoken Czech, co can refer to both things and people in relative clauses.

For example:

• To je člověk, co tam bydlí. = That’s the person who lives there.
• To je kniha, co chci číst. = That’s the book that I want to read.

In more formal Czech, people are more likely to use forms of který:

• To je člověk, který tam bydlí.
• To je kniha, kterou chci číst.

So yes, co is quite flexible in everyday speech.

The pattern is:

To je + noun phrase + relative clause

Here:

• To je = That is / This is
• ta kniha = the/that book
• co chci číst = that I want to read

So the sentence is built like this:

That is the book + that I want to read.

This is a very useful pattern in Czech. You can make many similar sentences:

• To je film, co chci vidět. = That’s the film I want to see.
• To je dům, co koupili. = That’s the house they bought.
• To je člověk, co ti pomůže. = That’s the person who will help you.