Learn Hardcore Dutch: Jammer dat de kantine vandaag dicht is. - Too bad that the cafeteria is closed today.

Jammer means “a pity/too bad.” It’s an adjective often used as an interjection. The full sentence behind it is Het is jammer dat…. Dutch commonly drops Het is and just says Jammer dat…. Both are natural:

Jammer dat de kantine vandaag dicht is.
Het is jammer dat de kantine vandaag dicht is.

Why does the verb is go at the end of dat de kantine vandaag dicht is?

Because dat introduces a subordinate clause. In Dutch, subordinate clauses push the finite verb to the end. Compare:

Main clause (V2): De kantine is vandaag dicht.
Subordinate clause: … dat de kantine vandaag dicht is.

What’s the difference between dat (that) as a conjunction and dat as a demonstrative?

Conjunction dat introduces a clause: Ik vind het jammer dat de kantine dicht is.
Demonstrative dat points to a thing: Dat gebouw heeft een kantine.
They’re spelled the same but function differently.

Should there be a comma after Jammer?

Not in Jammer dat…. You don’t need a comma between jammer and dat. If you use Jammer as a separate interjection, then a comma (or period) separates it from the next clause:

Jammer dat de kantine vandaag dicht is.
Jammer, de kantine is vandaag dicht.

Can I use helaas instead of jammer?

Often, yes, but they behave a bit differently:

Helaas = “unfortunately,” an adverb: Helaas is de kantine vandaag dicht.
Jammer = “a pity,” more like a judgment; it pairs naturally with dat: Het is jammer dat de kantine vandaag dicht is.
Tone: helaas can feel a bit more formal/neutral; jammer sounds more personal. In Belgian Dutch, spijtig is also common: Spijtig dat…

Is dicht the same as gesloten here?

Yes, both mean “closed,” with slight nuance:

dicht is very common in speech and signs: De kantine is dicht.
gesloten is a bit more formal or sign-like: De kantine is gesloten. Related verbs:
sluiten = to close (transitive): Ze sluiten de kantine om vijf uur.
dichtgaan = to close (intransitive): De kantine gaat om vijf uur dicht.

Does dicht also mean “near”? Could this sentence be misunderstood?

Dicht can mean “closed” or “tight,” and in combinations like dicht bij it means “close to/near.” On its own after a form of zijn, dicht means “closed,” not “near.”

De kantine is dicht. = closed
Ik woon dicht bij de kantine. = I live near the canteen

Why de kantine and not het kantine?

Kantine is a common-gender noun, so it takes de: de kantine. Many nouns ending in -e of Romance origin are de-words. You’d say een kantine, de kantine, not het kantine.

Is kantine the same as “cafeteria”? Are there other words?

Roughly, yes. Nuances:

de kantine: workplace/school canteen.
de cafetaria: a snack bar or informal eatery (not necessarily tied to a workplace).
het bedrijfsrestaurant: more formal company cafeteria/restaurant.
BE often also uses de mensa (university canteen).
Context decides the best choice.

Where should vandaag go? Can I move it?

In the subordinate clause, place it before the verb at the end:

Standard: … dat de kantine vandaag dicht is. Moving vandaag to the very end (… dicht is vandaag) is nonstandard in neutral prose (possible only as marked, afterthought emphasis). In a main clause you can front it:
Vandaag is de kantine dicht.

How can I say this more casually or more formally?

Casual: Jammer, de kantine is vandaag dicht. / Da’s jammer.
Emphatic: Wat jammer dat de kantine vandaag dicht is.
Neutral/formal: Het is jammer dat de kantine vandaag dicht is.

How do I change the tense (past/future)?

Keep the subordinate word order but change the verb:

Past: Jammer dat de kantine gisteren dicht was.
Future/plan: Jammer dat de kantine morgen dicht zal zijn. (Often simply: … morgen dicht is.)

Any quick pronunciation tips?

jammer: initial j like English y; stress on first syllable: YA-mmer.
kantine: stress on ti: kan-TI-ne; ie = long ee sound.
dicht: the ch is the Dutch guttural sound , like the German Bach; final t is pronounced.
dat: short a; final t is pronounced.