Děti si musí čistit zuby po večeři.

to have to

Breakdown of Děti si musí čistit zuby po večeři.

• po: after
• večeře: the dinner
• dítě: the child

Questions & Answers about Děti si musí čistit zuby po večeři.

Why is děti used here? What is the singular form?

Děti is the plural of dítě, which means child.

This is an irregular noun, so the plural is not something simple like adding an ending to the singular in an obvious way.

• singular: dítě = child
• plural: děti = children

In the sentence, Děti is the subject, so it is in the nominative plural.

Why is the verb musí the same form for a plural subject?

Because the verb muset has the same form in the 3rd person singular and 3rd person plural in the present tense.

So:

• on musí = he must / has to
• ona musí = she must / has to
• ono musí = it must / has to
• oni musí = they must / have to
• ony musí = they must / have to
• děti musí = children must / have to

This often surprises English speakers, because English also uses the same form in he must and they must, but learners may expect Czech plural agreement to look different. Here, it just happens that the forms are identical.

What does si mean in this sentence?