Au petit-déjeuner, les enfants se taisent enfin et mangent leur croissant.

The infinitive is se taire, which means to be quiet, to keep quiet, or to fall silent. It is an irregular verb, which is why se taisent may not look familiar at first.

In the present tense:

• je me tais
• tu te tais
• il / elle se tait
• nous nous taisons
• vous vous taisez
• ils / elles se taisent

So les enfants se taisent means the subject is they, which is why the form is se taisent.

Yes, se taire is a pronominal verb, so the se is part of the verb. In this sentence, you should learn it as a whole expression: se taire.

It is not always strongly reflexive in the English sense of themselves. It simply means to keep quiet or to fall silent.

This is important because taire without se is a different verb. Taire means to keep something unsaid or to conceal, as in taire la vérité. So here, you cannot just remove se.

Enfin means finally. Here it modifies se taisent, so the idea is that the children finally become quiet.

Its position is natural in French. Adverbs like enfin are often placed after the conjugated verb:

• les enfants se taisent enfin

That sounds more natural in French than putting enfin at the very beginning of that part of the clause.

Because the subject is les enfants, which is third person plural, the verb manger has to be conjugated as ils / elles mangent in the present tense.

So:

• les enfants mangent

This is the normal present-tense form for a regular -er verb with a plural subject.

No. In mangent, the ending -ent is not pronounced. So mangent sounds the same as mange.

This is very common with third person plural forms of French verbs:

• ils parlent
• elles regardent
• ils mangent

In all of these, the written -ent is silent.

Leur is singular because the noun after it, croissant, is singular. This usually suggests that each child has one croissant.

A very important rule is that leur / leurs agrees with the thing possessed, not with the number of owners:

• leur croissant = one croissant each, or one croissant belonging to them
• leurs croissants = more than one croissant

So even though les enfants is plural, leur is correct because croissant is singular here.