Möglet gör maten möglig.

Because möglet is the definite form of mögel.

In Swedish, definiteness is usually shown by adding an ending to the noun:

• mögel = mold
• möglet = the mold

So Möglet gör maten möglig refers to a specific mold, or to the mold already being talked about.

A more general statement is also possible:

• Mögel gör mat möglig = Mold makes food moldy

That sounds more like a general truth.

For the same reason: maten is the definite form of mat.

• mat = food
• maten = the food

So the sentence is talking about a particular food item or a specific batch of food, not food in general.

Compare:

• Möglet gör maten möglig = The mold makes the food moldy
• Mögel gör mat möglig = Mold makes food moldy

Swedish often uses the definite form where English would use the.

Here gör means makes in the sense of causes something to become a certain way.

It comes from the verb göra, which often means to do or to make.

In this sentence, the pattern is:

• X gör Y adjective
• X makes Y adjective

So:

• Möglet gör maten möglig
• The mold makes the food moldy

This is a very common Swedish structure.

Möglig is an adjective, and it describes the state that maten ends up in.

So the sentence structure is:

• Möglet = subject
• gör = verb
• maten = object
• möglig = object complement / result adjective

In other words, möglig tells you what the food becomes.

You can think of it like:

• The mold makes the food moldy
• not just does something to the food, but specifically causes it to be moldy

Because the adjective agrees with maten, and maten is singular common gender.

Swedish adjective agreement here works like this:

• common gender singular: möglig
• neuter singular: mögligt
• plural: mögliga

So:

• maten → möglig
• brödet → mögligt
• grönsakerna → mögliga

Examples:

• Möglet gör maten möglig.
• Möglet gör brödet mögligt.
• Möglet gör grönsakerna mögliga.

Yes. They come from the same root.

• mögel = mold
• möglig = moldy

This is a common pattern in Swedish: a noun and a related adjective are often closely connected.

Notice, though, that the spelling changes slightly:

• mögel
• möglig

The e disappears when the adjective is formed.

Yes. The pattern göra + object + adjective is very common.

It means that something causes something else to become a certain way.

Examples:

• Solen gör rummet varmt.
  The sun makes the room warm.

• Regnet gör vägen hal.
  The rain makes the road slippery.

• Det här gör mig glad.
  This makes me happy.

So Möglet gör maten möglig follows a very normal Swedish grammar pattern.

Yes, you could.

The difference is mainly specific versus general:

• Möglet gör maten möglig = specific mold, specific food
• Mögel gör mat möglig = mold in general, food in general

Both are grammatically fine. The version with -et and -en feels more like you are talking about a particular situation.

Because Swedish usually puts the definite article at the end of the noun as a suffix.

So instead of separate the words, Swedish often does this:

• mögel → möglet
• mat → maten

This is one of the biggest differences from English.

So in this sentence:

• -et in möglet = the
• -en in maten = the

The letter ö does not have an exact English equivalent.

A useful approximation is:

• say something a bit like the vowel in bird, but with rounded lips

A few pronunciation notes:

• gör has a soft g, pronounced like English y
• so gör sounds roughly like yur, but with Swedish ö, not a normal English vowel

In the other two words:

• möglet
• möglig

the g is pronounced as a normal hard g, because it is followed by l.

So the sentence has both:

• hard g in möglet and möglig
• soft g in gör

It is grammatically correct and understandable, and it sounds natural enough.

That said, it is also a bit neat and compact, so it could definitely appear in a textbook.

In everyday speech, someone might also say something like:

• Maten blir möglig av möglet.
• Det är mögel på maten.
• Maten har blivit möglig.

But Möglet gör maten möglig is still a perfectly good Swedish sentence, especially for showing how göra + object + adjective works.