W moim notatniku zapisuję nowe słowa, których chcę używać w pracy.

Because w means in here, and when w expresses location, it requires the locative case.

So:

• notatnik = notebook
• w notatniku = in the notebook

The adjective/pronoun mój also has to match that case:

• mój notatnik = my notebook
• w moim notatniku = in my notebook

So both words change because of the preposition w.

Zapisuję is:

• 1st person singular
• present tense
• from the imperfective verb zapisywać

It means something like I write down, I note down, or I record in writing.

In this sentence, it suggests a habitual or repeated action:

• I write down new words in my notebook

That is why the imperfective verb is natural here: it describes something you do regularly, not just one completed action.

Because zapisuję is more specific.

• pisać = to write
• zapisywać / zapisać = to write down, note down, record

So:

• piszę nowe słowa could sound like I am writing words
• zapisuję nowe słowa clearly means I write them down for later / I note them

In a sentence about vocabulary learning, zapisuję is the more natural choice.

Nowe słowa is the accusative plural, because it is the direct object of zapisuję.

You are writing down what? → new words

For these nouns:

• singular: słowo
• plural: słowa

Since słowo is an inanimate noun, its accusative plural looks the same as the nominative plural:

• nominative plural: nowe słowa
• accusative plural: nowe słowa

So even though it is the object, the form stays nowe słowa.

Because the relative pronoun has to match the case required inside the relative clause, not just the noun it refers to.

It refers to słowa, but in the clause:

• których chcę używać w pracy

the verb używać requires the genitive.

So we get:

• używać czego? = to use what? → genitive
• plural genitive form of the relative pronoun który = których

That is why you have:

• słowa, których chcę używać
• literally: words which/of which I want to use
• natural English: words that I want to use

If the verb required accusative, you might see które instead.

Yes. In standard Polish, używać normally takes the genitive.

Examples:

• używać komputera = to use a computer
• używać tego słowa = to use this word
• używać tych słów = to use these words

So in your sentence, the underlying idea is:

• chcę używać tych słów

When that becomes a relative clause, tych słów turns into których.

This is one of those verb patterns that English speakers usually just need to learn as a fixed rule:

• używać + genitive

Because Polish usually leaves out subject pronouns when the verb already makes the subject clear.

• zapisuję clearly means I write down
• the ending -ę tells you it is I

So ja is unnecessary unless you want emphasis or contrast.

Compare:

• Zapisuję nowe słowa. = I write down new words.
• Ja zapisuję nowe słowa, a on je tylko czyta. = I write down new words, and he only reads them.

Polish often drops pronouns where English keeps them.

This is a very common structure:

• chcę = I want
• używać = to use

So:

• chcę używać = I want to use

In Polish, after chcieć (to want), the next verb usually appears in the infinitive.

Other examples:

• chcę czytać = I want to read
• chcę pracować = I want to work
• chcę się uczyć = I want to study / learn

So this part of the sentence is grammatically straightforward:

• których chcę używać = which I want to use

It is the locative singular.

The noun is:

• praca = work

After w meaning in / at, you use the locative:

• w pracy = at work / in work

So:

• chcę używać w pracy = I want to use [them] at work

This phrase most naturally means at work, in my job, or in a work context.

Not exactly. W pracy most naturally means:

• at work
• in the workplace
• in a professional context

If you specifically wanted to say for work, Polish might use a different structure depending on the exact meaning, for example:

• do pracy = for work / to work
• w pracy = at work

In your sentence, w pracy means the words are ones you want to use while working or in your professional environment.

Because in Polish, a relative clause introduced by a form of który is normally separated by a comma.

So:

• nowe słowa, których chcę używać w pracy

The part after the comma gives extra information about słowa:

• which words?
• the ones I want to use at work

Polish punctuation is stricter than English here: this comma is expected.

Yes. Polish word order is fairly flexible, although different orders can sound more or less neutral or place emphasis in different spots.

Your sentence is a very natural, neutral version:

• W moim notatniku zapisuję nowe słowa, których chcę używać w pracy.

You could also say:

• Zapisuję w moim notatniku nowe słowa, których chcę używać w pracy.
• Nowe słowa, których chcę używać w pracy, zapisuję w moim notatniku.

These all mean roughly the same thing, but the emphasis shifts:

• starting with W moim notatniku emphasizes the location
• starting with Zapisuję emphasizes the action
• starting with Nowe słowa emphasizes what is being written down

So the original sentence is not the only possible order, but it is a perfectly natural one.

Not exactly, though both can be translated as notebook in English.

• notatnik = a notebook / notepad for notes
• zeszyt = an exercise book, school notebook, copybook

In this sentence, notatnik fits very well because the speaker is keeping notes of new words. It suggests a notebook used specifically for jotting things down.

It comes from który, which means which, who, or that in relative clauses.

Here are a few useful forms:

• który = nominative singular masculine
• które = nominative/accusative plural neuter or nominative plural non-masculine-personal
• których = genitive plural

So in this sentence:

• słowa, których chcę używać

the form których is chosen because:

1. it refers to a plural noun, and
2. the verb używać requires genitive.

This is a good example of how Polish relative pronouns change a lot depending on grammar.

Yes. The sentence uses the imperfective zapisywać because it describes a regular habit.

If you wanted a completed, one-time action, you would normally use the perfective verb zapisać.

Compare:

• zapisuję nowe słowa = I write down new words / I am writing down new words / I regularly write down new words
• zapiszę nowe słowa = I will write down the new words
• zapisałem nowe słowa = I wrote down the new words

So the original sentence sounds like a general learning habit, which is why zapisuję is the best choice.