Foten är redan undersökt.

Fot is the basic dictionary form, meaning foot.

Foten is the definite singular form, meaning the foot. In Swedish, the definite article is usually attached to the end of the noun:

• en fot = a foot
• foten = the foot

So Foten är redan undersökt starts with the foot, not just foot.

Because Swedish usually puts definiteness on the noun itself instead of using a separate word like English the.

So:

• foten = the foot
• not a separate word + fot

A separate definite word does appear when there is an adjective before the noun. For example:

• den undersökta foten = the examined foot

That structure is often called double definiteness:

• den
  • adjective + definite noun

But in your sentence, there is no adjective directly before foten, so foten by itself is enough.

Är is the present tense of vara (to be).

So:

• är = is / are

Here it combines with undersökt to describe the current state or result:

• är undersökt = is examined / has been examined already

Even if English often prefers has already been examined, Swedish can very naturally use är + participle to focus on the resulting state.

Undersökt is the past participle of undersöka, which means to examine or to inspect.

Basic forms:

• undersöka = to examine
• undersökte = examined (past tense)
• undersökt = examined (supine / past participle form)

In this sentence, undersökt works like a participle describing the foot’s condition after the examination.

So the structure is:

• Foten = the foot
• är = is
• redan = already
• undersökt = examined

Yes, it has a passive-like/resultative meaning.

The sentence does not name who examined the foot. It focuses on the foot and its current state.

Compare:

• Läkaren har redan undersökt foten.
  The doctor has already examined the foot.
  → active

• Foten är redan undersökt.
  The foot is already examined / has already been examined.
  → focus on the foot’s state/result

If you want a more clearly event-based passive, Swedish can also say:

• Foten har redan undersökts.
• Foten har redan blivit undersökt.

But är redan undersökt is very natural when the important point is that the examination is already done.

Because in a normal Swedish main clause, the finite verb usually comes early, and sentence adverbs like redan often come after that finite verb.

So the neutral order is:

• Foten
  • är
    • redan
      • undersökt

This is a very common pattern in Swedish.

Compare:

• Han är redan här. = He is already here.
• Boken är redan läst. = The book is already read / has already been read.

In a subordinate clause, the placement changes:

• Jag vet att foten redan är undersökt.
  I know that the foot has already been examined.

So:

• main clause: är redan
• subordinate clause: redan är

Yes. That is also grammatical.

The difference is mainly one of emphasis:

• Foten är redan undersökt
  focuses on the current state/result: the foot is in an already-examined state.

• Foten har redan blivit undersökt
  focuses more on the event/process of being examined.

• Foten har redan undersökts
  is another passive option, often a bit more formal or written.

In many real contexts, these can be translated similarly in English, but Swedish chooses among them depending on whether the speaker is thinking more about the result or the event.

Yes, it can.

In this sentence, undersökt is the form used with a singular noun here. But in plural or some adjective-like uses, you may see undersökta.

For example:

• Foten är undersökt.
  The foot is examined / has been examined.

• Fötterna är undersökta.
  The feet are examined / have been examined.

And before a definite noun:

• den undersökta foten
  the examined foot

So undersökt behaves a lot like an adjective or participle that can agree in form.

Yes, fot is irregular enough that it is worth memorizing.

Its common forms are:

• en fot = a foot
• foten = the foot
• fötter = feet
• fötterna = the feet

Notice the vowel change:

• fot → fötter

That is similar to English foot → feet, so it is actually a nice word to remember because both languages show an irregular change.

You move the finite verb to the first position:

• Är foten redan undersökt?
  Has the foot already been examined? / Is the foot already examined?

This is a standard Swedish pattern for yes/no questions:

• statement: Foten är redan undersökt.
• question: Är foten redan undersökt?

So the verb är comes before the subject foten.