Ona przypuszcza, że roślina potrzebuje wody.

Yes. In Polish, subject pronouns are often omitted because the verb ending usually already tells you who is doing the action.

So:

• przypuszcza = he/she/it assumes / supposes

That means Ona przypuszcza... and just Przypuszcza... can both be correct.

Including ona adds emphasis, contrast, or clarity. For example, it can suggest:

• She thinks so, not someone else.
• We want to be extra clear about who the subject is.

So in many contexts, Przypuszcza, że roślina potrzebuje wody would also be natural.

The base form is przypuszczać.

In this sentence, przypuszcza means:

• she supposes
• she assumes
• she suspects
• she thinks (in the sense of making a guess)

It usually suggests uncertainty rather than strong certainty. It is not as direct as simply stating a fact.

Conjugation in the present tense:

• ja przypuszczam = I suppose
• ty przypuszczasz = you suppose
• on/ona/ono przypuszcza = he/she/it supposes
• my przypuszczamy
• wy przypuszczacie
• oni/one przypuszczają

Because in Polish, a clause introduced by że normally takes a comma before it.

Here the sentence has two parts:

• Ona przypuszcza = She supposes
• że roślina potrzebuje wody = that the plant needs water

So the comma separates the main clause from the subordinate clause.

This is standard Polish punctuation:

• Myślę, że... = I think that...
• Wiem, że... = I know that...
• Ona przypuszcza, że... = She supposes that...

English sometimes drops that, but Polish normally keeps że in this kind of sentence.

Że means that.

It introduces a subordinate clause, just like English that in:

• She thinks that the plant needs water.

So:

• Ona przypuszcza = She supposes
• że roślina potrzebuje wody = that the plant needs water

A very common pattern in Polish is:

• verb of thinking/saying/knowing + że + clause

For example:

• Wiem, że... = I know that...
• Myślę, że... = I think that...
• Mówi, że... = He/She says that...

Roślina is in the nominative case, because it is the subject of the clause roślina potrzebuje wody.

The subject is the thing doing the verb action, or in this case the thing that has the need.

The dictionary form is also roślina, so here it has not changed.

Basic singular forms of roślina:

• nominative: roślina
• genitive: rośliny
• dative: roślinie
• accusative: roślinę
• instrumental: rośliną
• locative: roślinie

Since the plant is the subject, nominative is correct.

Because the verb potrzebować takes the genitive case, not the accusative.

The base noun is:

• woda = water

But after potrzebować, it becomes:

• wody = of water / water (genitive form)

So:

• potrzebować wody = to need water

This is something English speakers often have to memorize, because English does not show this kind of case change.

More examples:

• potrzebuję czasu = I need time
• potrzebujesz pomocy = you need help
• potrzebują pieniędzy = they need money

So in your sentence:

• roślina potrzebuje wody = the plant needs water

The base form is potrzebować = to need.

Potrzebuje is the third person singular present tense form, used with:

• on = he
• ona = she
• ono = it

Since roślina is singular and grammatically feminine, we use:

• roślina potrzebuje = the plant needs

Present tense forms of potrzebować:

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

So the ending matches the subject roślina.

Roślina is a grammatically feminine noun, which you can often tell from the ending -a in the singular dictionary form.

Yes, it matters for agreement in some situations, especially with:

• adjectives
• past tense verbs
• pronouns

In this sentence, it does not change the present-tense verb form, because potrzebuje is the same for he/she/it.

But you would see the feminine gender in other examples:

• ta roślina = this plant
• zielona roślina = a green plant
• roślina była sucha = the plant was dry

So gender is part of the noun’s grammar, even if it is not very visible in this exact sentence.

Yes, Polish word order is more flexible than English, because case endings and verb forms carry a lot of grammatical information.

The most neutral order here is:

• Ona przypuszcza, że roślina potrzebuje wody.

But you could also hear variations for emphasis, for example:

• Przypuszcza, że roślina potrzebuje wody.
• Ona przypuszcza, że wody potrzebuje roślina.
• Że roślina potrzebuje wody, ona przypuszcza.
  This is much less neutral and sounds stylistically marked.

Even though different orders are possible, not all of them sound equally natural in everyday speech. For learners, the original version is the safest one.

Polish does not have articles like English a/an and the.

So roślina can mean:

• a plant
• the plant

The exact meaning depends on context.

In your sentence, if the meaning shown to the learner is the plant, that interpretation comes from context, not from a separate word.

This is very normal in Polish. For example:

• Kupiłem książkę. = I bought a book / the book
• Kot śpi. = A cat is sleeping / The cat is sleeping

If Polish speakers need to be more specific, they often do it through context, word order, or extra words like:

• ta roślina = this plant
• jakaś roślina = some plant

A rough pronunciation guide:

• Ona ≈ OH-na
• przypuszcza ≈ pshi-POOSH-cha
• że ≈ zheh
• roślina ≈ rosh-LEE-na
• potrzebuje ≈ po-tsheh-BOO-yeh
• wody ≈ VO-dih

A few useful notes:

• rz often sounds like the zh in measure
• sz sounds like sh
• ś is a softer sound, somewhat like a softened sh
• ż sounds like zh
• w sounds like English v
• Polish stress is usually on the second-to-last syllable:
  • przy-PUSZ-cza
  • ro-ŚLI-na
  • potrze-BU-je

The cluster at the start of przypuszcza can feel difficult for English speakers, so it helps to say it slowly first and then speed up.

Not exactly.

• myśli = thinks
• przypuszcza = supposes / assumes / suspects

Przypuszcza usually sounds more like a guess or inference, with some uncertainty.

Compare:

• Ona myśli, że roślina potrzebuje wody.
  = She thinks the plant needs water.

• Ona przypuszcza, że roślina potrzebuje wody.
  = She supposes / assumes the plant needs water.

In many contexts they can be similar, but przypuszcza often sounds a bit more tentative or inferential.