It comes as no surprise that one of the most asked questions in the earlier stages of the course is about the "to" + Nominative vs „być” + Instrumental in sentences which I call „X is Y”. I’ll try to write a comprehensive guide here, so everything about this topic could be in one place.
So, the base for the translation is an English sentence that has an “X is Y” (or “X are Y”) construction.
PART ONE: WHEN BOTH X AND Y ARE NOUN PHRASES
One of the most common options is when both X and Y are noun phrases. Note – not necessarily nouns (“sandwich”), but noun phrases (“a big sandwich”). If that is the case, we have two ways that we can use to translate the sentence into Polish.
Option one is: X in Nominative + a form of ‘być’ (conjugation here) + Y in Instrumental.
Option two is: X in Nominative + 'to' + Y in Nominative.
You know the word ‘to’ as a neuter determiner ("to dziecko" = "this child"), but it is not the function that is serves here. In this context it will always be ‘to’ and won't change at all.
So on a simple example of “A dog is an animal.”:
1) Pies jest zwierzęciem.
2) Pies to zwierzę.
In plural (“Dogs are animals.”):
1) Psy są zwierzętami.
2) Psy to zwierzęta.
And now, an example with not just nouns, but noun phrases. Remember that not only adjectives can create noun phrases, but also for example articles, or pronouns like ‘this’. If you're not into linguistics enough to be sure that you know enough about noun phrases, read here.
So our example here will be:
This green piece of furniture is a wooden table.
1) Ten zielony mebel jest drewnianym stołem.
2) Ten zielony mebel to drewniany stół.
If we make it plural: These green pieces of furniture are wooden tables, we arrive at:
1) Te zielone meble są drewnianymi stołami.
2) Te zielone meble to drewniane stoły.
If the Y part is negated, we add „nie” in Polish. But where to add it? Well, it depends which option we are using. In the option number one, we negate the verb “to be”. So if for some reason we tried to claim that a dog is not in fact an animal, then it would be:
Pies nie jest zwierzęciem.
In option number two, we negate the Y part. So the same sentence would be:
Pies to nie zwierzę.
PART ONE AND A HALF: WHAT CAN ACTUALLY BE PUT INTO INSTRUMENTAL
Remember that it is important which part we will make "Y" and put into Instrumental. You can arrive at a sentence that is grammatically correct, but won't make sense semantically. Let me show it on geometry:
Każdy kwadrat jest prostokątem, ale nie każdy prostokąt jest kwadratem. (Every square is a rectangle, but not every rectangle is a square.)
"Kot jest zwierzęciem" (A cat is an animal) is okay, but "Zwierzę jest kotem" (An animal is a cat) is wrong. Not grammatically wrong, but semantically wrong. A specific animal can be a cat, but a totally general 'an animal' cannot, only some animals are cats.
"Paweł jest lekarzem" (Paul is a doctor) is obviously correct, but "Lekarz jest Pawłem" (A doctor is 'a' Paul) is really weird.
Sometimes the left noun phrase can be put in Instrumental, and the right be in Nominative (let's treat is as "Y is X"), but as you are learning, it's probably better to stick to the basic way, as this shows a change of focus. Anyway, the example that made me realize it needs adding to this guide was:
"Twoim zadaniem jest znaleźć wyjście." (Your task is to find an exit.)
Let's translate the Y part not as an infinitive, but as a gerund: "Your task is finding an exit". We now have four potential options to say that, depending on which part we want to stress: what is the task, or whose the task is.
The first two options will focus on 'what':
"Twoim zadaniem jest znalezienie wyjścia"
"Twoje zadanie to znalezienie wyjścia"
The other two focus on 'whose', and that it is 'a task':
"Znalezienie wyjścia jest twoim zadaniem"
"Znalezienie wyjścia to twoje zadanie"
Still, whether it's on the left side of the sentence or on the right, it's only the task that is put into Instrumental. So I think I'd say that it's the matter of what defines what. A definition of 'a cat', although a very simplified one, is that it is in fact 'an animal'. 'An animal' cannot however be defined as 'a cat'. Your task can be defined (precised) by saying that it is "to find the exit". It's hard, at least in Polish, to define "finding the exit" as being "your task". That's why only the task part can be in Instrumental, even if it's at the beginning of the sentence.
But there are sentences, when depending on the focus either of the noun phrases could be made Instrumental. Compare:
Mężczyzna jest mordercą (The man is a murderer)
So 'the man', therefore some man that was already mentioned (more probably "this man" = "ten mężczyzna") is a murderer.
Morderca jest mężczyzną. (The murderer is a man)
There is a murderer, but so far the only thing we know is that it's a man. This sentence could be possibly changed to "Mordercą jest mężczyzna", but it's better to focus on the more basic constructions now.
PART TWO: WHEN X IS A PERSONAL PRONOUN AND Y IS A NOUN PHRASE
Okay, so I hope that covers the most popular option. Now, another common thing is when X is a personal pronoun (I, you, they etc.) The only option that will sound natural then is option number one. DO NOT try to use option two, with ‘to’, here.
I am a man. = Ja jestem mężczyzną.
She is a beautiful woman. = Ona jest piękną kobietą.
They are her friends. = Oni są jej przyjaciółmi or One są jej przyjaciółkami.
(If the oni/one confuses you, see here and look for the distinction between masculine personal and not masculine personal.)
As the form of 'być' already implies the person, we usually omit the personal pronoun. It's probably 'the hardest' to omit it with 3rd person, as gender may not be obvious without it.
PART TWO AND A HALF: IF Y IS A NAME OR/AND A SURNAME
The main option for introducing yourself is literally "I call myself Y" = "Nazywam się Y", but there's also a possibility of using simple "I am". The Polish version will be somewhere between options one and two, actually. It has to be:
Personal pronoun + a form of 'być' + the name/surname in Nominative.
Yes, Nominative. Being "Mary" doesn't define you, you are "Mary". Being "a doctor" kind of defines you, so it goes into Instrumental. But here it has to be Nominative.**
Jestem Marek. = I'm Marek.
Jesteś Maria Nowak, prawda? = You're Maria Nowak, right?
Jesteśmy Nowakowie = We are the Nowaks (the Nowak family)
Jesteście Burdonowie, prawda? = You are the Burdons, right? (the Burdon family)
With 3rd person, both English and Polish should rather use "This is/These are" and not "He/She is/They are". Therefore:
To jest Tomasz. = This is Tomasz.
To są Kowalscy. = These are the Kowalskis (the Kowalski family)
** There's an exception in a weird construction such as "Because Mary was Mary, she obviously got angry" (Because of her character and because she's always 'herself', she got angry because she's a nervous person). You could use "Ponieważ Maria była Marią" here. The first "Mary" could probably even be simple "she" (and "ona" or omited in Polish). But that's completely on the side, as it's quite an unusual usage.
PART THREE: WHEN Y IS AN ADJECTIVE
Another situation will be, when X is a noun phrase (or a personal pronoun), but Y is an adjective. You should then use a 'mixed structure', just like in Part 2,5:
X in Nominative + a form of 'być' + the adjective in Nominative.
“This table is heavy” will translate as “Ten stół jest ciężki”.
“The women are beautiful” will translate to “Kobiety są piękne”.
“He is intelligent” will translate to “On jest inteligentny."
If negated, as this is option number one, ‘nie’ will be put before the form of ‘być’.
The only exception to this, that I found so far, is when you speak about your favourite colours. One could argue that the adjective denoting the colour is treated as a noun, therefore “My favourite colour is red” will be translated using option number two as:
“Mój ulubiony kolor to czerwony”.
It can be reversed to “Red is my favourite colour” and will result with:
“Czerwony to mój ulubiony kolor”.
Option number one could be used with the second sentence (“Czerwony jest moim ulubionym kolorem”) as Y is a noun phrase here, but not in the first one, where Y is an adjective. The negations would work the same way that I mentioned before.
PART FOUR: THIS IS Y
Another thing that sometimes causes problems is translating a very simple phrase built as “This is Y”.
As you can see, “this” doesn’t serve as a determiner here (like in “this boy”, “this animal”), but as a pronoun, which is in fact the subject of the sentence. In Polish, it will be translated as “To” – and of course, being the subject, “To” won’t change at all, no matter what gender we use, or whether it’s singular or plural.
It also doesn’t matter whether the English original sentence had “This/That/These/Those” – all of them will translate as “To”.
So showing this on some examples:
This is a dog. = To jest pies.
That is a good idea! = To jest dobry pomysł!
These are very fast cars. = To są bardzo szybkie samochody.
Those are red books = To są czerwone książki.
In such sentences, the form of ‘być’ is actually optional, you can omit it. So is the case with the 3rd person options for names/surnames. In my opinion sometimes the sentence can look a bit weird without the 'być', if it's very short (To pies), but I have no problem at all with "To dobry pomysł!"
And of course in negation, ‘nie’ will go before the form of ‘być’, even if it’s actually omitted (“To nie (jest) pies.”)
PART FOUR AND A HALF: WHEN Y IS AN ADJECTIVE/ADVERB
If you have a construction “This is Y” or “That is Y” and Y is an adjective, in Polish you obviously need “To jest”, and the adjective is neuter singular.
This is interesting. = To (jest) interesujące/ciekawe.
That is just stupid. = To (jest) po prostu głupie.
It is not obligatory to use “jest” and in fact, sentences with some adjectives seem more natural with “jest”, and some without it. You cannot just use “Jest” without “To” here.
If Y is an adverb, then the sentence is in fact subjectless in Polish. In English, it should probably start with “It”. This is then some kind of general “it”, which doesn’t really mean anything specific.
It is cold. = Jest zimno.
Na dworze jest gorąco. = It is hot outside.
W naszej szkole jest nudno. = It is boring in our school.
There isn’t any “to” in Polish, as there is no real subject.
PART FIVE: WHEN X IS AN ADVERB OF TIME/PLACE AND Y IS A NOUN PHRASE
I saw problems arrising when X was an adverb, at least an adverb of time (today, yesterday, tomorrow, etc.). Such a situation calls for a mixed construction, similar to the one in Part 2.5 with names.
X (Adverb) + a form of 'być' + Y in Nominative.
The only form of 'być' that makes sense here is 3rd person, so either singular "jest" or plural "są".
Dzisiaj jest niedziela. (Today is Sunday.)
W przyszłym miesiącu są egzaminy. (In the next month, there are exams.)
W poniedziałek są urodziny Moniki. (On Monday there's Monika's birthday).
Tu jest Polska, tu się pije! (Here is Poland, one drinks here!)
Tam jest jaskinia. (There is a cave there.)
PART SIX: THE WORDPLAY
The last thing that comes to my mind, that I saw on Duolingo once, is the kind of a sentence which is more of a wordplay than a real description of something. So for example “A good sofa is a comfortable sofa”, or “A good enemy is a dead enemy”.
Such a situation calls for the option number two, number one would sound really weird here. Therefore the translations will be, respectively:
Dobra sofa to wygodna sofa.
Dobry wróg to martwy wróg.
Well, I guess that’s it. If you notice something that I missed, or maybe some mistake that I made, please don’t hesitate to comment and I will add/correct it.
Resource: https://forum.duolingo.com/comment/16373167
Author: https://www.duolingo.com/profile/Jellei