Nowe słownictwo wydaje mi się trudne, ale chcę je zapamiętać.

Because słownictwo is a neuter singular noun in Polish.

That means any adjective describing it must also be neuter singular:

• nowy = masculine singular
• nowa = feminine singular
• nowe = neuter singular

So:

• nowe słownictwo = new vocabulary

The same thing happens later in the sentence with trudne:

• trudne słownictwo = difficult vocabulary

In Polish, słownictwo is a singular collective noun. It refers to vocabulary as a whole, not to individual words.

So Polish treats it like one thing:

• To słownictwo jest trudne. = This vocabulary is difficult.

If you want to talk about individual words, you would usually use:

• słowa = words
• wyrazy = words/expressions
• słówka = little words / vocabulary items (very common in learning contexts)

So:

• Nowe słownictwo = new vocabulary
• Nowe słowa = new words

Wydaje mi się literally means something like it seems to me or it appears to me.

The structure is:

• wydaje się = seems / appears
• mi = to me

So:

• Nowe słownictwo wydaje mi się trudne
  = The new vocabulary seems difficult to me
  = more natural English: The new vocabulary seems difficult to me or I find the new vocabulary difficult

This is a very common Polish pattern:

• To wydaje mi się dziwne. = That seems strange to me.
• Ten pomysł wydaje mi się dobry. = This idea seems good to me.

They do different jobs.

• mi = to me (dative pronoun)
• się = part of the verb expression wydawać się / wydać się, meaning to seem

So wydaje mi się is not really I give myself or anything like that. It is just the standard Polish way to say seems to me.

Compare:

• wydawać = to give out / to issue / to spend, depending on context
• wydawać się = to seem

So się is essential here because it changes the meaning of the verb.

Both are understandable, but wydaje mi się is the most natural and common order.

In Polish, short unstressed words like mi, ci, mu, się often appear in a preferred clitic order. In everyday Polish, mi się sounds very natural.

So:

• wydaje mi się = standard, natural
• wydaje się mi = possible, but less natural in normal speech

As a learner, it is best to memorize:

• wydaje mi się
• wydaje ci się
• wydaje mu się

Again, it agrees with słownictwo, which is neuter singular.

So:

• trudny = masculine singular
• trudna = feminine singular
• trudne = neuter singular

Because słownictwo is neuter:

• słownictwo jest trudne
• słownictwo wydaje mi się trudne

Je means it here, and it refers back to słownictwo.

This can confuse learners because je is also used for them in some contexts. But here it is singular neuter accusative, referring to słownictwo.

So:

• chcę je zapamiętać = I want to memorize it

Pronoun reference:

• słownictwo = neuter singular
• accusative form of ono = je

Examples:

• To słownictwo jest trudne, ale chcę je zrozumieć.
• To zadanie jest trudne, ale zrobię je.

This is an important aspect difference.

• pamiętać = to remember, to have in memory
• zapamiętać = to memorize, to learn so that you will remember

So in this sentence:

• chcę je zapamiętać means I want to memorize it / learn it well enough to remember it

Compare:

• Pamiętam to słowo. = I remember this word.
• Chcę zapamiętać to słowo. = I want to memorize this word.

So zapamiętać focuses on the process of getting something into your memory.

After chcę (I want), Polish normally uses the infinitive.

So:

• chcę zapamiętać = I want to memorize
• chcę przeczytać = I want to read
• chcę zrozumieć = I want to understand

If you said zapamiętuję, that would mean I am memorizing, which is a finite verb form and does not fit after chcę in this structure.

Because the speaker means they want to successfully memorize the vocabulary, as a complete result.

In Polish:

• zapamiętać = perfective, one completed result
• zapamiętywać = imperfective, the ongoing/repeated process of memorizing

So:

• Chcę je zapamiętać. = I want to memorize it / learn it by heart
• Staram się je zapamiętywać. = I am trying to keep memorizing it / work on memorizing it

After chcę, both aspects are sometimes possible, but they mean slightly different things. Here, the perfective form is very natural because the goal is the completed result.

Yes, absolutely — but the meaning is slightly different.

• Nowe słownictwo jest trudne. = The new vocabulary is difficult.
  This sounds more direct and objective.

• Nowe słownictwo wydaje mi się trudne. = The new vocabulary seems difficult to me.
  This sounds more personal, subjective, and a bit softer.

So wydaje mi się is often used when you want to express an impression rather than a hard fact.

Because ale means but, and in Polish it normally introduces a new clause, so it is preceded by a comma.

So:

• Nowe słownictwo wydaje mi się trudne, ale chcę je zapamiętać.

This is standard Polish punctuation.

Yes, Polish word order is flexible, but different orders sound more or less natural depending on emphasis.

The original sentence is very natural:

• Nowe słownictwo wydaje mi się trudne, ale chcę je zapamiętać.

Possible variations:

• Mi nowe słownictwo wydaje się trudne, ale chcę je zapamiętać.
  Stronger emphasis on to me
• Nowe słownictwo trudne mi się wydaje...
  Possible in poetic or marked style, but not a good default for learners

So the best version to learn first is the original one.

Both are possible, but they sound a little different.

• słownictwo = vocabulary, more general or abstract
• słówka = words/vocab items, very common in language-learning contexts

So:

• Nowe słownictwo wydaje mi się trudne. = The new vocabulary seems difficult to me.
• Nowe słówka wydają mi się trudne. = The new words/vocab items seem difficult to me.

Notice that with słówka, the grammar changes because słówka is plural:

• nowe słówka
• wydają mi się trudne
• chcę je zapamiętać

So the pronoun je stays, but the verb changes to plural: wydają instead of wydaje.