Learn Hardcore Czech: V pondělí pracuji celý den.

The preposition v (“in/on”) normally takes locative for static position in space or time.
However, the noun pondělí is a neuter noun ending in -í, and for these nouns many cases have the same form as the nominative.

So:

Nominative: pondělí (Monday)
Locative: v pondělí (on Monday) – the form looks identical

You can see that it really does decline when used with a different preposition:

do pondělí – until Monday (genitive)
od pondělí – from Monday (genitive)

So: grammatically, it’s locative; it just happens to look the same as the basic form.

Why does the sentence omit já? Can I say Já v pondělí pracuji celý den?

Czech usually drops subject pronouns (já, ty, on, etc.) because the verb ending already shows the person.

pracuji / pracuju – “I work / I am working”

So V pondělí pracuji celý den is completely natural and normal.

You can say Já v pondělí pracuji celý den, but then:

já is stressed/emphatic: “I work all day on Monday (as opposed to someone else).”

For a neutral statement, you normally omit já.

What’s the difference between pracuji and pracuju?

Both mean “I work / I am working”, present tense, 1st person singular of pracovat.

pracuji – more formal, written, textbook style
pracuju – more colloquial, everyday spoken Czech

In speech, most people say:

V pondělí pracuju celý den.

In formal writing (essays, official documents), you’ll more often see:

V pondělí pracuji celý den.

Both are correct; the choice is mainly style / register.

Does pracuji mean “I work (regularly)” or “I will work (this Monday)”? How do Czechs understand this?

Pracuji is a present tense of an imperfective verb (pracovat), so it naturally describes:

Habitual action:
- V pondělí pracuji celý den.
  = On Mondays I (usually) work all day.
  (Often used if it’s part of your regular schedule.)
Scheduled near future (context-dependent):
- If you’re talking about next Monday’s plan, people can understand it as
  “This Monday I’m working all day,” similar to English “I work on Monday” for timetables.

If you want to be clearly future and one specific Monday, you’d usually say:

V pondělí budu pracovat celý den. – I will work all day on Monday.

So the original sentence is slightly ambiguous; context decides whether it’s habitual or a specific future plan.

What does celý den literally mean, and why is it in that form?

Celý den literally means “the whole day / all day”.

den – day (nominative)
celý den – whole day (nominative)
In the sentence pracuji celý den, celý den is actually in the accusative case, used as an “accusative of duration”.

Czech uses the accusative to express how long something lasts:

Pracuji celý den. – I work all day.
Čekal jsem dvě hodiny. – I waited two hours.
Spali jsme celou noc. – We slept all night.

So celý den is accusative expressing duration, not an object.

Can I change the word order, e.g. Celý den v pondělí pracuji or Pracuji v pondělí celý den?

Yes, Czech word order is flexible, but it changes emphasis / information structure.

Some possible variants (all grammatically correct):

V pondělí pracuji celý den.
– Neutral: “On Monday I work all day.”
(Monday is the context.)
V pondělí celý den pracuji.
– Emphasis that the whole day is spent working, still with Monday as context.
Celý den v pondělí pracuji.
– Stronger focus on “the whole day on Monday” as a block of time.
Pracuji celý den v pondělí.
– Sounds less natural; v pondělí normally appears toward the beginning if it’s the time frame.

The most neutral and idiomatic choice is exactly your original:

V pondělí pracuji celý den.

How do you pronounce pondělí?

Pondělí is pronounced approximately like “PON-dye-lee”.

Key points:

po – like “po” in “position” (short o).
nďe – dě here is pronounced as ďe (a palatalized “dy-eh” sound).
- So pon-ďe ≈ “pon-dye”.
lí – long í, like “ee” in “see”, but longer: “lee”.

Stress in Czech is always on the first syllable, so:

PON-dye-lee (ˈponɟɛliː)

Also note: the ď sound (written as ď or produced by dě/di) doesn’t exist in English; it’s a soft “d” pronounced with the tongue closer to the hard palate.

How do you pronounce pracuji?

Pracuji is pronounced roughly like “PRA-tsoo-yi”.

Breakdown:

pra – “pra” as in “pram”, short a.
cu – c in Czech is always pronounced ts, so cu = “tsoo”.
ji – j is like English y in “yes”, so ji = “yi”.

Altogether: PRA-tsu-yi, with stress on the first syllable: PRA-tsu-yi (ˈpratsuji).

Is there any change in pronunciation of v in v pondělí?

Yes, in connected speech, the v before a word starting with p is often pronounced like f.

So instead of clearly saying [v pondělí], many speakers say something close to:

[f pondělí]

This is called assimilation: the v is influenced by the following p.
Both a careful [v pondělí] and a more natural [f pondělí] are fine; the second just sounds more fluent and native-like.

Why aren’t days of the week capitalized in Czech? Should it be Pondělí?

In Czech, days of the week are not capitalized unless they start a sentence:

pondělí, úterý, středa, čtvrtek, pátek, sobota, neděle

So in the middle of a sentence you write:

V pondělí pracuji celý den.
V pátek mám volno.

You only use a capital letter at the beginning of the whole sentence, never because it’s a day name.

Does Czech have articles like “a” or “the” for den (“day”) in celý den?

No, Czech has no articles (no words like “a”, “an”, “the”).

So:

celý den can mean “(the) whole day” or “all day”, depending on context.
There is no separate form for “a whole day” vs. “the whole day”.

The meaning is understood from context, not from a word like “the”.
That’s why the sentence can be translated either as:

I work the whole day on Monday.
or
On Monday I work all day.

without any change in the Czech.