La retumilo ĉesis funkcii dum la interrompo.

Retumilo is a compound Esperanto word.

• ret- relates to the internet / network
• umi is a general-purpose verb ending often used in words like retumi, meaning to browse the internet / surf the web
• -ilo means tool / instrument

So retumilo literally means a tool for browsing, which is why it means browser.

This kind of word-building is very common in Esperanto, and learning the parts can make vocabulary much easier to remember.

Yes. La is the definite article in Esperanto, and it works roughly like English the.

So:

• la retumilo = the browser
• la interrompo = the interruption

A few useful things about la:

• It does not change for singular or plural.
• It does not change for gender.
• It stays la no matter what role the noun has in the sentence.

Esperanto has no separate word for English a/an, so an indefinite noun often appears with no article at all.

This is an important distinction.

• ĉesi = to stop, to come to an end
• ĉesigi = to make something stop, to cause something to stop

In the sentence, the browser itself stopped functioning, so ĉesis is correct:

• La retumilo ĉesis funkcii = The browser stopped functioning

If you said ĉesigis, that would mean something like caused to stop, so you would normally need an object:

• La interrompo ĉesigis la retumilon = The interruption stopped the browser

So ĉesis is the intransitive form, and ĉesigis is the causative/transitive form.

Because Esperanto often uses a structure like:

• ĉesi + infinitive = to stop doing something
• komenci + infinitive = to begin doing something
• daŭrigi + infinitive = to continue doing something

So:

• ĉesis funkcii = stopped functioning

Here:

• ĉesis is the finite verb in the past tense
• funkcii stays in the infinitive because it expresses the action that stopped

This is very similar to English stopped working / stopped functioning, though Esperanto uses the infinitive more directly.

Because the root is funkci-, and the infinitive ending is -i.

So:

• funkcii = funkci- + i = to function

It may look unusual because there are two i's in a row, but that is completely normal in Esperanto. The first i is part of the root, and the second i is the infinitive ending.

Other forms are:

• funkcias = functions / is functioning
• funkciis = functioned / was functioning
• funkcios = will function

Dum means during.

So:

• dum la interrompo = during the interruption

After dum, you normally do not use -n, because dum is a preposition, and prepositions in Esperanto usually take the basic noun form, not the accusative.

So this is correct:

• dum la interrompo

not:

• dum la interrompon

The -n ending is mainly used for direct objects and for certain expressions of direction.

Interrompo is a noun meaning interruption.

It comes from the root interromp-, related to interrupting or breaking continuity, plus the noun ending -o:

• interrompi = to interrupt
• interrompo = interruption

This is another example of Esperanto’s regular word-building:

• -i for the verb
• -o for the noun

So if you know one form, you can often recognize the others easily.

Yes, that is possible, but the meaning is slightly different.

• La retumilo ĉesis funkcii dum la interrompo
  = The browser stopped functioning during the interruption

  This focuses on the moment or event of stopping.

• La retumilo ne funkciis dum la interrompo
  = The browser was not functioning during the interruption

  This focuses on the state of not working during that time.

So ĉesis funkcii emphasizes the change, while ne funkciis emphasizes the condition.

Esperanto word order is fairly flexible, but the basic order here is the most natural:

• La retumilo ĉesis funkcii dum la interrompo.

This follows a clear pattern:

• subject: La retumilo
• verb: ĉesis
• infinitive complement: funkcii
• time phrase: dum la interrompo

You could move dum la interrompo for emphasis:

• Dum la interrompo la retumilo ĉesis funkcii.

That still means the same thing, but it puts more focus on the time expression.

The letter ĉ is pronounced like English ch in church.

So:

• ĉesis sounds roughly like CHEH-sis

A few pronunciation notes:

• Esperanto letters are pronounced consistently
• e is like e in met
• stress usually falls on the second-to-last syllable

So:

• ĉe-sis → stress on ĉe
• re-tu-MI-lo
• funk-ci-I
• in-ter-ROM-po

That regular stress pattern is one of the helpful features of Esperanto.

Because Esperanto uses regular endings to show the part of speech.

• -o = noun
• -i = infinitive verb
• -as = present tense verb
• -is = past tense verb
• -os = future tense verb

So in this sentence:

• retumilo is a noun: browser
• ĉesis is a past-tense verb: stopped
• funkcii is an infinitive verb: to function
• interrompo is a noun: interruption

These endings are a core part of Esperanto grammar and help you understand sentences quickly.