Learn Hardcore Danish: Det betyder, at maden er klar.

Det is a “dummy” or formal subject, similar to English that or it in That means… / It means….
It doesn’t refer to maden; it refers to a previous situation, sentence, or idea in the context (something you’ve just been talking about).
In Danish, you normally need an explicit subject, so you can’t just start with Betyder, at maden er klar – you must have Det.

Why is the verb betyder used here, and how is it different from mener or vil sige?

betyder = means in the sense of signifies / has this meaning.
You use betyder for words, signs, situations: Hvad betyder det? – What does it mean?

mener = mean in the sense of intend / think / have this opinion:

Hvad mener du? – What do you mean / what’s your opinion?

vil sige (in det vil sige): roughly that is to say / in other words.
In your sentence you could also say Det vil sige, at maden er klar, which sounds a bit like you’re rephrasing or clarifying something.

What exactly is at doing in at maden er klar? Is it like English to or that?

Here at is a conjunction meaning that, introducing a subordinate clause:

Det betyder, at maden er klar. – That means (that) the food is ready.

Danish at has two main uses:

Conjunction “that”: Jeg tror, at han kommer. – I think (that) he’s coming.
Infinitive marker “to”: at spise – to eat.

In your sentence it is “that”, not “to”.
Unlike English, you normally cannot drop at here; Det betyder, maden er klar is wrong.

Why is there a comma before at? Do I always need one?

Danish has two accepted comma systems. In the traditional (grammatical) system, you put a comma before at when it starts a subordinate clause, so:

Det betyder, at maden er klar. ✅

In the newer (less grammatical) system, you may leave some of these commas out, so you might also see:

Det betyder at maden er klar. ✅ (also correct in modern Danish)

Many Danes still use the comma before at, and as a learner it’s safe and common to keep it there when at starts a clause like this.

Why is it maden and not something like den mad for the food?

Danish usually puts the at the end of the noun as a suffix instead of using a separate word like English the.

mad = food
maden = the food

So maden literally means food‑the.
You don’t say den mad for the food in standard Danish; you say maden.

What does the ending -en in maden tell me about the noun?

The suffix -en marks two things at once:

Singular
Definite (the)
Common gender (also called “n‑gender” or “utrum”)

So from maden you can see that mad is a common gender noun (en mad in the dictionary), not a neuter noun (et …).
Neuter nouns take -et in the definite: hus → huset (house → the house).

Could I just say Maden er klar by itself? Does it mean something different?

Yes. Maden er klar on its own simply states: The food is ready.

Your full sentence Det betyder, at maden er klar adds an extra step:

Something (earlier in the conversation) means something.
What it means is: the food is ready.

So Maden er klar is the direct statement; Det betyder, at maden er klar explains that some other sign, phrase, or situation has that meaning.

What exactly does klar mean here, and how is it different from færdig?

In this context klar means ready / prepared, like English The food is ready (to eat).

Difference in nuance:

klar: ready for use / for the next step.
- Maden er klar. – The food is ready (served or about to be served).
færdig: finished, done (the process is completed).
- Maden er færdig. – The food is done (cooking is finished).

For food, both can be used, but klar focuses on “ready for you now”, and færdig focuses more on “the making/cooking is finished”.

Is the word order maden er klar the same in a subordinate clause as in a main clause?

Yes, in this simple case the word order is the same: subject – verb – complement.

Main clause:

Maden er klar. – subject maden, verb er, complement klar.

Subordinate clause after at:

at maden er klar – still subject maden, verb er, complement klar.

The difference between main and subordinate clauses in Danish word order shows up mainly with adverbs/negation, e.g.:

Main: Maden er ikke klar.
Subordinate: at maden ikke er klar.

Can I leave out at the same way English often leaves out that?

No, not in standard Danish.
In English, That means (that) the food is ready is fine with or without that.

In Danish you normally must include at to introduce this kind of clause:

Det betyder, at maden er klar. ✅
Det betyder, maden er klar. ❌ (wrong)

So when translating English that‑clauses (especially after verbs like betyde, tro, sige, mene, vide), keep at.

How is Det betyder, at maden er klar pronounced in normal speech?

Very roughly (ignoring some tricky Danish details), you might hear something like:

Det ≈ deh (often short and unstressed)
betyder ≈ be-TU-ðer (the d is a soft th‑like sound)
at ≈ at (often quite weak)
maden ≈ MA-ðn (the d again is soft; the final -en is reduced)
er ≈ er (very short, can sound almost like just ə)
klar ≈ klar with a long a (something like British “klaa”)

Spoken smoothly, it might sound like one connected chunk, with Det betyder running together and maden er almost merging to maden-er.