Learn Hardcore Polish: Kiedy piszę szybko na klawiaturze, mój kot goni mysz na ekranie. - When I type quickly on the keyboard, my cat chases the mouse on the screen.

Polish has one present tense for both English “I write” and “I am writing”. So piszę can mean either, depending on context. Here, context makes it clear that it means “I (am) type(ing)”.

Why is kiedy followed by the present tense (piszę), and what nuance does that give?

Kiedy means “when”.

With the present tense here – kiedy piszę szybko na klawiaturze – it expresses a general, repeated situation:

“When(ever) I type quickly on the keyboard…”

So this is something that typically happens each time you type fast, not one specific future or past event.

Compare:

Kiedy piszę szybko, mój kot goni mysz.
= Whenever I type fast, my cat chases the mouse. (a general habit)
Kiedy będę pisać szybko, mój kot pewnie też będzie gonił mysz.
= When I will be typing fast, my cat will probably also chase the mouse. (more about a particular future situation)

You can also use gdy instead of kiedy in this sentence. It’s a bit more formal/literary, but the meaning here would be the same.

Why is it na klawiaturze and not just klawiatura or na klawiaturę?

The phrase is na klawiaturze – literally “on the keyboard”.

na
- locative case is used for location (where?):
  - na klawiaturze – on the keyboard (where I’m typing)
  - na ekranie – on the screen

The noun klawiatura (keyboard) changes to the locative form klawiaturze after na when it means “on” in the sense of being located on a surface.

Contrast:

na klawiaturze – on the keyboard (static location, as in this sentence)
na klawiaturę – onto the keyboard (movement towards the keyboard, accusative case), e.g.
- Położyłem ręce na klawiaturę. – I put my hands onto the keyboard. (less natural than na klawiaturę → na klawiaturze here, but shows the idea)

In this sentence we’re talking about the place where the typing happens, so it has to be the locative: na klawiaturze.

Why do we say mój kot and not just kot? Could we drop mój?

Mój kot means “my cat”.

Polish has no articles (a / the), so kot by itself is just “cat” with no built-in idea of “the cat” or “my cat”.

mój kot – my cat
kot – a/the cat (but without specifying whose)

In many situations, if it’s clear from context whose cat it is, you can drop the possessive and just say kot. For example, if you’ve already established that you’re talking about your cat.

In this isolated sentence, adding mój makes the meaning clear: it’s not just any random cat; it’s my cat.

What does the verb goni mean, and how is it different from other “chase” verbs like ścigać?

Goni is the 3rd person singular present of gonić, which means “to chase / to run after”.

Infinitive: gonić – to chase
on/ona/ono goni – he/she/it chases, is chasing

Here it has a playful, simple meaning: the cat is visually “chasing” the mouse cursor on the screen.

Compared with other verbs:

ścigać – to pursue, to chase (often more serious: police chasing a criminal, racers chasing each other)
biegać za – to run after (more literally “to run after something/someone”)

For a cat chasing a mouse, gonić is the most natural everyday verb.

What is the gender and case of mysz here, and why doesn’t it change form (e.g. myszę)?

Mysz is:

feminine noun
In this sentence, it is in the accusative singular: mysz

The pattern is:

Nominative (dictionary form): mysz – a/the mouse
Accusative singular (direct object): mysz – (chases) the mouse

So nominative = accusative for this noun in the singular. That’s why you don’t see a change like myszę.

The verb gonić takes a direct object in the accusative, so we get:

mój kot goni mysz – my cat chases the mouse

Why is it na ekranie and not something like w ekranie? What case is ekranie?

Ekran means “screen”.

Basic form (nominative): ekran
Locative singular: ekranie

After na with the meaning “on (a surface)”, we use the locative:

na ekranie – on the screen

We wouldn’t say w ekranie here, because w means “in/inside”, and the mouse cursor isn’t inside the screen in the spatial sense – it is displayed on the surface of the screen.

So:

na ekranie – on the screen (correct for this context)
w ekranie – literally “in the screen” (unusual; would sound strange here)

Can the word order change, for example: Mój kot goni mysz, kiedy piszę szybko na klawiaturze? Does it change the meaning?

Yes, you can change the word order without changing the basic meaning.

Possible versions:

Kiedy piszę szybko na klawiaturze, mój kot goni mysz na ekranie.
Mój kot goni mysz na ekranie, kiedy piszę szybko na klawiaturze.

Both mean essentially the same: When I type quickly on the keyboard, my cat chases the mouse on the screen.

Differences are mainly in what you present first:

Starting with kiedy… highlights the condition/time first.
Starting with mój kot… puts focus on what the cat does, and then you explain when that happens.

Within each clause, the word order is fairly fixed here (e.g. mój kot goni mysz), but Polish is still more flexible than English. You could sometimes move adverbs around, e.g. kiedy szybko piszę na klawiaturze, without changing the core meaning.

What aspect or nuance does goni have? How would this differ from a perfective form?

Gonić is an imperfective verb. The form goni describes:

an ongoing or repeated action: the cat is (in general) chasing, or tends to chase, the mouse.

In this sentence, that fits well because we’re describing a typical, repeated behavior: whenever you type fast, the cat chases the cursor.

A perfective counterpart (something like pogonić) would focus on the action as completed (“to chase away once, to give a chase so that it’s over”), which wouldn’t fit the habitual, ongoing sense here.

So:

goni – (is) chasing / chases (ongoing/habitual)
a perfective form would suggest one completed chase, not the usual behavior.

Polish doesn’t use articles like “a” or “the”. How does that affect phrases like kot and mysz in this sentence?

Polish has no articles (a, an, the). Nouns like kot and mysz are bare forms.

Their meaning (a cat / the cat / my cat, etc.) comes from:

context
possessive pronouns (like mój)
sometimes word order or stress

In this sentence:

mój kot – clearly “my cat” (possessive pronoun)
mysz – could be understood as “the mouse” or “a mouse”, but from context (a computer screen) it’s really “the mouse cursor”, the only one present.

So where English must choose between a and the, Polish simply uses the noun and relies on context to supply that information.