Potrzebuję większego stołu.

Because the verb potrzebować usually takes the genitive case in Polish.

• dictionary form: stół = table
• genitive singular: stołu

So:

• Potrzebuję stołu = I need a table
• not Potrzebuję stół

This is one of the first case patterns learners usually notice in Polish: after potrzebować, the thing needed is normally in the genitive.

For the same reason: the adjective has to match the noun it describes.

Since stołu is:

• genitive
• singular
• masculine

the adjective must also be:

• genitive
• singular
• masculine

So:

• nominative: większy stół = a bigger table
• genitive: większego stołu = of a bigger table / a bigger table after potrzebuję

Polish adjectives agree with nouns in case, number, and gender.

The dictionary forms are:

• potrzebuję → potrzebować = to need
• większego → większy = bigger / larger
• stołu → stół = table

So the sentence is built from:

• potrzebować
• większy
• stół

but those words change form because of grammar.

Potrzebuję is 1st person singular, so it means I need.

It comes from potrzebować:

• ja potrzebuję = I need
• ty potrzebujesz = you need
• on/ona potrzebuje = he/she needs
• my potrzebujemy = we need
• wy potrzebujecie = you all need
• oni/one potrzebują = they need

In Polish, the subject pronoun ja is usually omitted, because the verb ending already shows who the subject is.

Yes. It is grammatically correct.

• Potrzebuję większego stołu.
• Ja potrzebuję większego stołu.

Both mean the same thing, but adding ja gives extra emphasis, like:

• I need a bigger table

Most of the time, Polish leaves out the pronoun unless you want contrast or emphasis.

Because większy is a comparative form.

The basic adjective is:

• duży = big

The comparative is:

• większy = bigger / larger

So:

• duży stół = a big table
• większy stół = a bigger table

Polish often uses a different word stem for the comparative, not just a predictable ending added to the basic adjective.

No, you do not have to say it.

In Potrzebuję większego stołu, the comparison is understood from context:

• bigger than the current table
• bigger than this one
• bigger than what I have now

If you want to say the comparison explicitly, you can:

• Potrzebuję większego stołu niż ten. = I need a bigger table than this one.

But very often Polish, like English, leaves that unstated.

A rough guide is:

po-tsheh-BOO-yeh VYENK-sheh-go STOH-woo

A few useful pronunciation notes:

• rz in potrzebuję sounds like the zh sound in measure
• ę in większego is often pronounced more like en before consonants, so więk- sounds roughly like vyenk-
• sz sounds like sh
• ł in stołu sounds like English w

So stołu sounds roughly like STOH-woo.

Stół is masculine.

Yes, that matters, because adjectives in Polish must agree with the noun’s:

• gender
• number
• case

That is why you get:

• większy stół in nominative
• większego stołu in genitive

If the noun were feminine or plural, the adjective form would be different.

Yes, but the neutral, most natural order here is:

• Potrzebuję większego stołu.

Polish word order is more flexible than English because case endings show grammatical relationships. You might also hear:

• Większego stołu potrzebuję.

That version sounds more marked or emphatic, as if stressing a bigger table.

So learners should normally use:

• Potrzebuję większego stołu.

In standard Polish, that is the normal pattern learners should remember:

• potrzebować + genitive

Examples:

• Potrzebuję czasu. = I need time.
• Potrzebujemy pomocy. = We need help.
• Potrzebujesz nowego telefonu. = You need a new phone.

So większego stołu fits that same pattern.

You would say:

• Potrzebuję dużego stołu.

Compare:

• Potrzebuję dużego stołu. = I need a big table.
• Potrzebuję większego stołu. = I need a bigger table.

Again, both dużego and większego are in the genitive because of potrzebuję.

Because stół is a masculine noun, and its genitive singular form is stołu.

This is something you largely have to learn with the noun pattern:

• nominative: stół
• genitive: stołu

Not every masculine noun forms the genitive in exactly the same way, so it is best to learn nouns together with important case forms when possible.

Yes. Potrzebować covers the general idea of to need. Depending on context, English might translate it as:

• I need
• I require

But in everyday speech, I need is usually the best match.

So Potrzebuję większego stołu most naturally means:

• I need a bigger table.

Yes. Stół is the normal word for a table, especially a dining table, work table, or general table.

A related word is:

• stolik = small table / little table / coffee table

So:

• Potrzebuję większego stołu = I need a bigger table
• Potrzebuję większego stolika = I need a bigger small table / coffee table

The choice depends on what kind of table you mean.