być in the Present: jestem, jesteś… | Polish Grammar

If you learn one verb perfectly before any other, make it być ("to be"). It is irregular — its forms do not follow any of the regular conjugation classes — and it sits underneath enormous amounts of Polish: it states who you are, where you are, whether something exists, and it later serves as the auxiliary for the future and the passive. The good news is that there are only six forms, and once you internalise the single most important fact about być — that what comes after it changes case depending on what kind of word it is — you avoid the most common beginner error in the language.

The six forms

There is no shortcut here: być is suppletive (its stem changes shape across the paradigm), so you simply memorise these six. The 3rd person plural są is the one beginners forget most — it is not built from jest.

Person	być	Meaning
ja	jestem	I am
ty	jesteś	you are (sg, informal)
on / ona / ono	jest	he / she / it is
my	jesteśmy	we are
wy	jesteście	you are (pl, informal)
oni / one	są	they are

Watch the diacritics closely. Four of the six forms carry an ś (jesteś, jesteśmy, jesteście) and the plural is są with a nasal ą, not sa. Writing jestes or sa is a spelling error, not a typo — the soft ś and the nasal ą are different sounds.

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Because Polish drops subject pronouns (the verb ending already tells you the person), you will far more often say Jestem zmęczony than Ja jestem zmęczony. Add ja only for contrast or emphasis: Ja jestem gotowy, a ty? — "I'm ready, what about you?"

Use 1: identity and roles — the instrumental predicate

Here is the fact that separates learners who studied Polish properly from those who didn't. When być links the subject to a noun naming a role, profession, or category, that noun goes into the instrumental case, not its dictionary (nominative) form. So "I am a student" is Jestem studentem — never Jestem student. English has nothing like this; "a teacher" looks the same whether it follows "is" or not. In Polish, the noun after być wears a special ending precisely because it is a predicate.

Jestem nauczycielem, uczę matematyki w liceum.

I'm a teacher, I teach maths at a secondary school.

Moja siostra jest lekarką w szpitalu na Pradze.

My sister is a doctor at the hospital in Praga.

Oni są studentami, więc mają zniżki na bilety.

They're students, so they get discounts on tickets.

The instrumental endings are covered in full on the instrumental predicate page; the takeaway for now is that być + a role noun = instrumental.

Use 2: descriptions — the adjective stays nominative

By contrast, when być links the subject to an adjective (describing a quality, not naming a category), the adjective stays in the nominative and simply agrees in gender and number with the subject. This is the split that trips people up: Jestem studentem (noun → instrumental) but Jestem zmęczony (adjective → nominative). And because the adjective agrees, a man says zmęczony and a woman says zmęczona for the same "I'm tired."

Jestem bardzo zmęczona, idę spać.

I'm very tired, I'm going to bed. (woman speaking)

Czy jesteś głodny? Zrobiłem kolację.

Are you hungry? I've made dinner.

Te jabłka są jeszcze zielone, kup inne.

These apples are still green, buy different ones.

So być has two different completions for the two main kinds of word that follow it: nouns take the instrumental, adjectives take the nominative. Get this contrast firmly and you have solved most of the verb.

Use 3: location

For location, być behaves the way English speakers expect — the place is expressed with a preposition (most often w "in" or na "on/at") plus its case, and być just sits there as a plain link verb. No instrumental on the place name; the preposition governs the case.

Jestem w domu, możesz przyjść.

I'm at home, you can come over.

Gdzie jesteście? Czekamy na was od dwudziestu minut.

Where are you? We've been waiting for you for twenty minutes.

Klucze są na stole w kuchni.

The keys are on the table in the kitchen.

Use 4: existence — "there is / there are"

Polish has no separate "there is/are" verb; być does the job. In the affirmative, jest means "there is" and są means "there are." Word order tends to put the existing thing after the verb.

Jest problem z ogrzewaniem w całym bloku.

There's a problem with the heating in the whole building.

Są jakieś pytania, czy możemy kończyć?

Are there any questions, or can we finish?

The negative — and the trap of nie ma

Negating być with nie is straightforward for identity, description, and location: just put nie in front. Nie jestem gotowy ("I'm not ready"), Nie jesteśmy w domu ("We're not home"). But existence is different, and this is the second big być trap.

To say something does not exist or is not present, Polish does not use nie jest. It uses a suppletive, frozen form: nie ma (literally "[it] has not"), and crucially the thing that is absent goes into the genitive case. So the positive Jest mleko ("There's milk") negates to Nie ma mleka ("There's no milk") — mleko → mleka.

Nie ma chleba, muszę iść do sklepu.

There's no bread, I have to go to the shop.

Nie ma go w pracy, wziął wolne.

He's not at work, he took the day off.

Niestety nie ma już biletów na ten koncert.

Unfortunately there are no more tickets for this concert.

Notice nie ma never changes for number: it covers both "there isn't" and "there aren't." The full story — including how nie ma is borrowed from mieć, not być — is on the absence and nie ma page.

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być has three different "completions": a role noun goes instrumental (jestem lekarzem), an adjective stays nominative (jestem chory), and to say something is absent you switch to nie ma + genitive (nie ma czasu). Deciding which one you need before you open your mouth is the whole game.

być as an auxiliary

Beyond these uses, być is the building block for two larger structures you will meet soon. The future of imperfective verbs is być in the future (będę, będziesz, będzie…) plus the infinitive or the past participle — będę czytać / będę czytał ("I will read") — covered on the być future page. And the passive uses być (or zostać) plus a passive participle: Dom jest sprzedany ("The house is sold"). For now, just register that the verb you are drilling here is load-bearing far beyond simple "to be" sentences.

Będę w biurze do piątej, zadzwoń wcześniej.

I'll be in the office until five, call before then.

Common Mistakes

❌ Jestem nauczyciel.

Incorrect — a role noun after być must be instrumental: nauczycielem.

✅ Jestem nauczycielem.

I'm a teacher.

❌ Oni jest moimi przyjaciółmi.

Incorrect — the 3pl of być is są, not jest.

✅ Oni są moimi przyjaciółmi.

They are my friends.

❌ Nie jest mleka w lodówce.

Incorrect — existential negation uses nie ma + genitive, not nie jest.

✅ Nie ma mleka w lodówce.

There's no milk in the fridge.

❌ Jestem zmęczonym po pracy.

Incorrect — an adjective after być stays nominative: zmęczony/zmęczona, not instrumental.

✅ Jestem zmęczony po pracy.

I'm tired after work.

❌ Jestes gotowy?

Incorrect spelling — the 2sg is jesteś, with a soft ś.

✅ Jesteś gotowy?

Are you ready?

Key Takeaways

The six forms: jestem, jesteś, jest, jesteśmy, jesteście, są — memorise są specially; it is not built from jest.
A role noun after być takes the instrumental (jestem inżynierem); an adjective stays nominative and agrees (jestem chory / chora).
Location uses a preposition + case; być is just the link (jestem w pracy).
Existence is jest / są; but non-existence is the suppletive nie ma + genitive (nie ma czasu), never nie jest.
być later becomes the auxiliary for the future and the passive, so the effort here pays off repeatedly.

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