Potrzebuję nożyczek i taśmy, żeby zamknąć tę kopertę.

Because the verb potrzebować / potrzebuję normally takes the genitive case in Polish.

So after potrzebuję (“I need”), the nouns change form:

• nożyczki → nożyczek
• taśma → taśmy

This is one of the first things learners notice, because in English need does not change the noun, but in Polish it does.

More examples:

• Potrzebuję czasu. = I need time.
• Potrzebuję wody. = I need water.
• Potrzebuję pieniędzy. = I need money.

Yes. Nożyczki is one of those nouns that are normally used only in the plural, just like scissors in English.

So:

• dictionary form: nożyczki
• after potrzebuję: nożyczek

This is similar to English:

• These scissors are sharp not
• This scissor is sharp (except in special technical uses)

Other Polish plural-only nouns include:

• drzwi = door
• spodnie = trousers
• okulary = glasses

Tę kopertę is in the accusative singular feminine.

That is because it is the direct object of zamknąć (“to close / shut / seal”).

Both the demonstrative and the noun must match in:

• gender
• number
• case

So:

• nominative: ta koperta = this envelope
• accusative: tę kopertę = this envelope (as the object)

That is why both words change:

• ta → tę
• koperta → kopertę

In standard Polish grammar, after a verb as a direct object, the correct accusative feminine singular form is tę.

So:

• Zamknąć tę kopertę = correct standard Polish

Many native speakers say tą kopertę in everyday speech, but traditionally that form is considered non-standard in careful written Polish.

So as a learner, it is best to use:

• tę kopertę
• tę książkę
• tę torbę

Here żeby means in order to / so that.

In this sentence:

• Potrzebuję nożyczek i taśmy, żeby zamknąć tę kopertę. = I need scissors and tape in order to close/seal this envelope.

About the alternatives:

• żeby = very common, natural, everyday
• aby = more formal or literary
• by = shorter, often used in some structures, but not always interchangeable in exactly the same way for beginners

For a learner, żeby is the safest and most useful choice in ordinary conversation.

Because zamknąć is the perfective infinitive, and here the speaker means a completed result: closing/sealing the envelope successfully.

Polish often uses:

• perfective for one completed action or intended result
• imperfective for ongoing, repeated, or general activity

So:

• zamknąć = to close, to shut, to get it closed
• zamykać = to be closing, to close repeatedly, to close in a general/process sense

In this sentence, the idea is:

• I need scissors and tape so that I can get this envelope closed

That is why zamknąć fits better.

Yes, literally zamknąć means to close/shut, but with things like envelopes it can naturally cover the idea of closing/sealing them too, depending on context.

Because the sentence mentions tape, the intended meaning is clearly something like:

• close up the envelope
• seal the envelope shut

So although the literal core meaning is close, the natural English translation may be seal in this context.

Because in Polish, subordinate clauses are normally separated by a comma, and żeby introduces a subordinate clause.

So:

• Potrzebuję nożyczek i taśmy, żeby zamknąć tę kopertę.

This comma is standard and expected in Polish writing.

English is often less strict in similar short to-infinitive structures, so this may feel unusual to English speakers.

Yes. Polish word order is fairly flexible, because case endings show the grammatical relationships.

The given sentence is very natural:

• Potrzebuję nożyczek i taśmy, żeby zamknąć tę kopertę.

But other versions are possible, for example:

• Żeby zamknąć tę kopertę, potrzebuję nożyczek i taśmy.
• Nożyczek i taśmy potrzebuję, żeby zamknąć tę kopertę.

The meaning stays very similar, but the emphasis changes:

• starting with Żeby zamknąć tę kopertę... emphasizes the purpose
• starting with Nożyczek i taśmy... emphasizes what is needed

Yes. You can say:

• żeby zamknąć kopertę = to close/seal an envelope
• żeby zamknąć tę kopertę = to close/seal this envelope

Including tę makes it specific: a particular envelope.

Without tę, the phrase is more general or less specific.

A rough pronunciation guide:

• potrzebuję ≈ po-tsheh-BOO-yeh
• żeby ≈ ZHEH-bih

A few useful sound notes:

• rz usually sounds like the zh in measure
• ż has a similar zh sound
• ę at the end of tę is often pronounced less strongly than learners expect, sometimes close to te in fast speech, though the spelling remains tę
• j in Polish sounds like English y in yes

So:

• Potrzebuję nożyczek i taśmy, żeby zamknąć tę kopertę can be approximated as:
• po-tsheh-BOO-yeh no-ZHI-chek ee TASH-mih, ZHEH-bih zam-knohnch ten kopert-en

That is only an approximation, but it can help at the start.

Yes. Taśma is a general word for tape, but like English tape, the exact type depends on context.

It can refer to things like:

• adhesive tape
• packing tape
• ribbon-like strip material
• tape in technical contexts

Here, because the speaker wants to close an envelope, taśma is understood as some kind of adhesive tape.

If you want to be more specific, Polish can do that too, for example:

• taśma klejąca = adhesive tape
• taśma pakowa = packing tape

So in this sentence, taśmy simply means some tape in the genitive after potrzebuję.