Na de behandeling mocht de patiënt uitrusten.

It is a time phrase meaning after the treatment.

• na = after
• de behandeling = the treatment

So this phrase tells you when the patient was allowed to rest.

Because behandeling is a de-word in Dutch.

Dutch nouns usually take either de or het as their definite article:

• de behandeling = the treatment
• het huis = the house

Unfortunately, whether a noun takes de or het often has to be learned with the noun itself. A useful clue here is that nouns ending in -ing are very often de-words, so behandeling follows a common pattern.

This is because Dutch main clauses normally follow the verb-second rule.

In this sentence, Na de behandeling is placed first for emphasis or style. Once that happens, the finite verb must still come second:

• Na de behandeling = first element
• mocht = second position
• de patiënt = subject comes after the verb

So:

• Na de behandeling mocht de patiënt uitrusten.

If you begin with the subject instead, you get:

• De patiënt mocht na de behandeling uitrusten.

Both are correct.

Mocht is the past tense singular of mogen.

• mogen = to be allowed to / may
• ik/hij/zij mocht = I/he/she was allowed to
• wij/jullie/zij mochten = we/you/they were allowed to

So here mocht agrees with the singular subject de patiënt.

In this sentence, mocht means was allowed to.

That is a very common use of mogen in Dutch: permission.

So the idea is not uncertainty, but permission:

• De patiënt mocht uitrusten = the patient was allowed to rest

Depending on context, mocht can sometimes feel like could or might, but here permission is the natural reading.

Because uitrusten is an infinitive used with the modal verb mocht.

In Dutch main clauses with a modal verb such as mogen, kunnen, willen, moeten, the finite modal comes earlier in the sentence, and the other verb goes to the end:

• De patiënt mocht uitrusten.
• Hij kon slapen.
• Zij wilde vertrekken.

So mocht is the conjugated verb, and uitrusten stays in the infinitive at the end.

Because after a modal verb like mogen, Dutch uses a bare infinitive.

So you say:

• mocht uitrusten
• kan komen
• wil eten
• moet gaan

not:

• mocht te uitrusten ❌

This is similar to English, where you say can go rather than can to go.

Uitrusten means to rest, to take a rest, or to recover by resting.

It often suggests resting in order to regain strength or recover after effort, illness, or treatment.

Rusten exists too, but it is less common in everyday speech for this meaning and can sound more formal or different depending on context. For a person recovering after a treatment, uitrusten is very natural.

Also, uitrusten is a separable verb:

• infinitive: uitrusten
• main clause with conjugation: Hij rust uit
• with a modal: Hij mag uitrusten

So in your sentence, the full infinitive stays together at the end.

Yes, absolutely.

Both of these are correct:

• Na de behandeling mocht de patiënt uitrusten.
• De patiënt mocht na de behandeling uitrusten.

The difference is mainly focus:

• Na de behandeling... puts the time phrase first, so it emphasizes when
• De patiënt... starts with the subject, which is a more neutral order

The two dots in patiënt are a diaeresis. They show that the vowels should be pronounced separately, rather than as one combined sound.

So patiënt is pronounced roughly as three parts:

• pa
• ti
• ent

The dots help show that the final part is separate. Without them, a learner might be tempted to read the vowels incorrectly.

You will also see this in the plural:

• patiënten = patients

Yes. It is:

• de patiënt = the patient

This is another noun that takes de, not het. Its plural is:

• de patiënten

So both singular and plural use de.

Good question. Separable verbs are only split in certain sentence structures.

For example:

• De patiënt rust uit.
  Here the verb is conjugated, so the prefix separates.

But with an infinitive after a modal verb, it stays together:

• De patiënt mocht uitrusten.

So:

• rust uit = split form
• uitrusten = whole infinitive

That is why your sentence uses uitrusten as one word.

In a subordinate clause, Dutch usually sends the finite verb to the end.

For example:

• Ik hoorde dat de patiënt na de behandeling mocht uitrusten.

Here dat introduces a subordinate clause, and the verbal part goes to the end of that clause.

So this is a useful contrast:

• main clause: Na de behandeling mocht de patiënt uitrusten.
• subordinate clause: ... dat de patiënt na de behandeling mocht uitrusten.

That difference in word order is very important in Dutch.