Mi brosas miajn dentojn ĉiutage.

In Esperanto, -as is the present-tense verb ending. The dictionary form is brosi = to brush, and brosas means brush / am brushing depending on context.

In this sentence, because of ĉiutage, it clearly means a habitual action: I brush my teeth every day.

The dictionary form is brosi.

Esperanto verbs always have predictable endings:

• -i = infinitive, as in brosi = to brush
• -as = present, brosas
• -is = past, brosis
• -os = future, brosos

So when you look up brosas, you remove -as and get brosi.

The -n marks the direct object, called the accusative.

In Mi brosas miajn dentojn:

• Mi is the subject, the person doing the action.
• brosas is the verb.
• dentojn is what is being brushed, so it is the direct object.

That is why dentoj becomes dentojn.

Because miajn has to agree with dentojn.

Words like mia behave like adjectives in Esperanto, so they match the noun in:

• number: singular or plural
• case: whether it has the accusative -n

So:

• mia dento = my tooth
• miaj dentoj = my teeth
• mian denton = my tooth as a direct object
• miajn dentojn = my teeth as a direct object

That is why both words show plural, and both show the accusative.

Because the sentence is talking about teeth, not a tooth.

Esperanto normally states number directly and literally:

• mian denton = my tooth
• miajn dentojn = my teeth

Since people usually brush more than one tooth, the plural is the natural choice here.

ĉiutage is an adverb meaning every day or daily.

It is built from the idea of ĉiu tago = every day, but here it functions as a single adverb, so it describes how often the action happens.

A very similar alternative is ĉiun tagon. Both are correct:

• Mi brosas miajn dentojn ĉiutage.
• Mi brosas miajn dentojn ĉiun tagon.

The first is a single adverb; the second is a noun phrase meaning literally every day.

Because possessives like mia, via, lia, and so on already make the noun definite.

So Esperanto normally says:

• miaj dentoj = my teeth

not:

• la miaj dentoj

This is similar to English, where you say my teeth, not the my teeth.

Yes. Esperanto word order is fairly flexible, especially with adverbs.

These are all natural:

• Mi brosas miajn dentojn ĉiutage.
• Ĉiutage mi brosas miajn dentojn.
• Mi ĉiutage brosas miajn dentojn.

The first one is straightforward and neutral. Moving ĉiutage can slightly change emphasis, but the basic meaning stays the same.

You do not always have to include it, but including it is clear and very natural.

Sometimes Esperanto can leave out a possessive if the owner is obvious from context, especially with body parts or very familiar situations. But for a learner, miajn dentojn is the safest and clearest form.

So:

• Mi brosas miajn dentojn = definitely I brush my teeth
• Mi brosas la dentojn might be understood from context, but it is less explicit

Yes. brosi means to brush.

The related noun is broso = a brush. This is a common Esperanto pattern:

• broso = a brush
• brosi = to brush

So Mi brosas miajn dentojn uses the ordinary verb for brushing.