Polish language: the Vocative case

Vocative (Pol. wołacz) is the seventh grammatical case in the Polish language, with which many foreigners struggle. That is due to its relative rarity in other languages and divergence of core idea and actual use in modern Polish.
I will skip how do you form such words, as those are present in dictionaries, and focus on when to use it, which is often described incorrectly. You will learn how to talk in a polite way, and how to use and interpret Polish insults.
Core idea behind the vocative
Word changes its form into the vocative form when its used to directly call the person you currently talk to. Base word form (nominative) is then used when talking about someone, not to someone.
When to use it in Polish
This finds a number of uses that I will describe, but the difference is biggest with insults, when using or not using the vocative is the difference between talking about x word when you talk to someone, and actually directly launching it against that person. After all, it is a colossal difference if you talk “about a whore” or call someone one! Polishes marks the difference by grammar! It is also used with titles such as “professor”. You could therefore say that the vocative then is used in Polish to damage or to add to someone’s honour.
In Polish specifically (not in other languages), using vocative for common names fell out of use already. Perhaps this is the first step of that grammatical feature falling out of use entirely (as it did in modern Russian), in some hundred years or so.
So for names like “Ania” (female), “Kasia” (famale), “Michał” (male), “Rafał” (male) – while vocative forms are known – you would not use them.
✓ Good: “Ania! Chodź” (Ania, come!)
✗ Bad: “Aniu! Chodź” Our grandma was talking like that to my sister, but in modern Polish, such usage of vocative fell out of use.
Similarly, with male names:
✓ Good: “Rafał! Chodź” (Rafał, come!)
✗ Bad: “Rafale! Chodź” This sounds so archaic that it has some medieval or Biblical feel to it.
So when to use it, for real this time
However, if used in tandem with some titles, you do use vocative. Easiest practical example is in class, in schools, in public office, in business.
✓ Good: “Pani Aniu, proszę podejść.” (Mrs. Ania, please come closer.) Please also notice that “chodź” (=come, command) turned into way more polite “proszę” (=please) + infinitive of a more fancy word, you can translate those as “please approach”.
✗ Bad: “Pani Ania, proszę podejść.“ When native speakers say this, there is something rude about it. It’s a bit like the person talking (teacher, perhaps) has so little respect to Ania that she talks to her in 3rd person, not even caring to address directly. But you will also see this wrong form used by foreigners, notably Russian-speaking teachers from Ukraine or Russia, because modern Russian simply lost this feature of grammar.
And again, for male forms:
✓ Good: “Panie Rafale, proszę podejść.” (Mr. Rafał, please approach.)
✗ Bad: “Pan Rafał, proszę podejść.” This sounds broken and when native speakers use it, it sounds rude, like they’re mocking you. That rudeness is really not felt when foreigners say it (so don’t get stressed), but it would sound broken.
Of course nothing with Polish is ever simple and there is some odd phenomenon where plain male names in vocative forms are used as nominative. This is colloquial to a massive degree, but widespread and has been around for quite a while. It gets ultra confusing for foreigners, but it is literally what I just described: vocative forms used as common nominative just for shits and giggles of street folk. Examples:
▸ “Stachu poszedł do domu” (Staszek went home).
▸ “Grzechu ma gorączkę” (Grzegorz has fever).
That is more complex. Those aren’t just vocatives of “Staszek” and “Grzegorz”, which would be “Staszku”, “Grzegorzu”, but they’re vocatives out of their augmentative forms “Stach”, “Grzech”. Augmentative is a rare form that is the opposite of diminutive, while diminutives (dog-doggy, bird-birdie) are used to make something sound small, nice and cute, augmentatives do exactly opposite. This is perhaps why this phenomenon happens only for male names and it sounds like some street chav speech. So the “Stach” and “Grzech” have vocative forms “Stachu” and “Grzechu”, and those went right at the start of the loop to become base forms. Why – I don’t know. Perhaps this is the part of Polish society that simply drinks the heaviest.
Insults or vulgarisms
Now the fun part. I remember in Russian train a bunch of children were calling me “durak!” (they were thinking I couldn’t understand them, I explained to them that I do in Russian and they went red-faced and quiet). Just “Durak, durak!” while looking me in the eyes. I couldn’t understand what they want with this idiot, but it took a while for me to get that they were calling me that. The word durak in Russian means an idiot and is equivalent to Polish dureń. You would never use dureń like this.
✓ Good: “Ty durniu!” (You idiot!)
✗ Bad: “Ty dureń!”
Remember those are vocatives, so when you use such forms, you are pulling the trigger, so you better be ready to face the consequences. If you just want to talk about someone, you use the basic form (nominative form):
✓ Good: “Co to za dureń?” (Who is this idiot?)
✗ Bad: “Co to za durniu?” This sounds so broken most native speakers wouldn’t be linguistically creative to make it up. This feeling is so strong because “durniu” is vocative, it’s used only to directly address someone, and the rest of the sentence (“who is this x”) collides with such purpose.
Let’s get more examples, because insults are fun, and you must know them so that you know when you are being insulted.
✓ Good: “Kurwo.” (You whore.) This is extremely heavy. Never use this yourself, even if you like insults, this one is beyond a certain line you should not cross.
✓ Good, but a different meaning: “Kurwa!” (Fuck!) This doesn’t call anyone, it’s the trash word you use when you hit a table with your foot.
Also, you can get creative:
✓ Good: “Chodź, barani łbie.” (Come, you ram’s head.) “Łeb” is specifically animal’s head, usually of cattle or a dog, hence the insulting power.
✗ Bad: “Chodź, barani łeb.” Sounds broken.
Other languages
It is a feature mostly of European languages. Most Slavic languages use vocative, such as Serbo-Croatian or Ukrainian, but not Russian anymore (there are some traces of it, compare “Бог”-“Боже”). In Ukrainian, you also have “dureń” (in Cyrillic “дурень”) with vocative as in Polish (“дурню”).
Latin language had it. Compare “dominus” (lord) – “domine!” (oh lord!), and “lupus” (wolf) – “lupe!” (hey, wolf!). Same with classical Greek, “κυριος” (lord), “κυριε” (Christians will recognise this in “Kyrie eleison” – “Lord, forgive me!”), same with wolf: “λυκος“–“λυκε“.
Outside European languages, apparently Georgian and Korean have it too.