Mi ne naĝos hodiaŭ, ĉar la kuracistino diris, ke mi devas ripozi ankoraŭ unu tagon.

Naĝos has the ending -os, which marks the future tense in Esperanto.

• naĝas = is swimming / swims
• naĝos = will swim

So Mi ne naĝos hodiaŭ means I will not swim today, not I am not swimming right now.

In Esperanto, tense is shown very regularly by the verb ending:

• -as = present
• -is = past
• -os = future

In Esperanto, ne usually goes directly before the word or part of the sentence it negates.

So:

• Mi ne naĝos hodiaŭ = I will not swim today

This is the normal placement. English speakers sometimes want to think in terms of do not / will not, but Esperanto does not use helper verbs like do in the same way. You simply put ne before the verb:

• Mi naĝas = I swim / am swimming
• Mi ne naĝas = I do not swim / am not swimming

Ĉar means because. It introduces the reason for the first part of the sentence.

• Mi ne naĝos hodiaŭ = I will not swim today
• ĉar ... = because ...

So the structure is:

I will not swim today, because ...

It is a very common conjunction in Esperanto.

Esperanto often uses commas to separate clauses more clearly than English sometimes does.

In this sentence:

• Mi ne naĝos hodiaŭ, ĉar ...
• ... diris, ke ...

The comma before ĉar separates the main clause from the because clause.

The comma before ke separates the reporting verb diris from the clause that follows: ke mi devas ripozi ...

This punctuation is very normal in Esperanto.

Kuracistino means female doctor.

It breaks down like this:

• kurac- = treat medically / heal
• -ist- = professional, practitioner
• -in- = female
• -o = noun ending

So:

• kuracisto = doctor
• kuracistino = female doctor

The la means the, so la kuracistino = the female doctor.

A learner should notice that Esperanto builds words very systematically.

Yes, you could say kuracisto if you do not want to specify that the doctor is female.

• kuracisto = doctor
• kuracistino = female doctor

In modern Esperanto, many speakers use the basic profession word when sex is not important, and use -in- only when they want to make it explicit.

So both are possible depending on what you want to express.

Because the sentence reports something said earlier, but the obligation is still valid now.

• diris = said
• devas = must / have to

So the idea is:

• the doctor said this earlier
• what she said is: I must rest one more day

Esperanto often keeps the tense that matches the actual meaning of each clause, rather than changing everything mechanically.

Compare:

• Ŝi diris, ke mi devas ripozi. = She said that I have to rest.
• Ŝi diris, ke mi devis ripozi. = She said that I had to rest.

The first suggests the obligation still applies; the second puts the obligation more fully in the past.

Ke means that and introduces a subordinate clause.

• la kuracistino diris, ke mi devas ripozi = the doctor said that I must rest

In Esperanto, ke is normally used where English sometimes optionally drops that.

English:

• She said that I must rest.
• She said I must rest.

Esperanto strongly prefers:

• Ŝi diris, ke mi devas ripozi.

So yes, in a sentence like this, ke is generally expected.

After modal verbs like devi (must / have to), Esperanto uses the infinitive, not a second finite verb.

So:

• devas ripozi = must rest

Not:

• devas ripozas ❌

This works much like English:

• I must rest
• not: I must rests

Other examples:

• Mi volas dormi. = I want to sleep.
• Ŝi povas veni. = She can come.
• Ni devas atendi. = We must wait.

Here tagon has the accusative ending -n because it expresses duration of time.

• unu tago = one day
• unu tagon = for one day / one day long

So:

ripozi ankoraŭ unu tagon means to rest for one more day

This is a common Esperanto use of the accusative: not only for direct objects, but also for time expressions showing duration.

Examples:

• Mi atendis du horojn. = I waited for two hours.
• Li laboris la tutan nokton. = He worked all night.

Ankoraŭ means still, yet, another, one more, depending on context.

Here:

• unu tagon = one day
• ankoraŭ unu tagon = one more day / another day

So the doctor is saying the speaker needs to rest for one additional day.

This is a very common use of ankoraŭ.

Examples:

• Mi ankoraŭ atendas. = I am still waiting.
• Donu al mi ankoraŭ unu minuton. = Give me one more minute.

Yes, Esperanto word order is fairly flexible, although some orders sound more natural than others.

The original:

Mi ne naĝos hodiaŭ, ĉar la kuracistino diris, ke mi devas ripozi ankoraŭ unu tagon.

You could also say, for example:

• Hodiaŭ mi ne naĝos, ĉar la kuracistino diris, ke mi devas ripozi ankoraŭ unu tagon.

That puts more emphasis on today.

However, because Esperanto relies less on word order and more on endings, many rearrangements are grammatically possible. Still, the original version is very natural and clear.

Yes. Hodiaŭ means today, and here it functions as a time adverb.

It does not need any special ending:

• Mi laboras hodiaŭ. = I am working today.
• Hodiaŭ estas varme. = It is warm today.

Unlike tagon, which has -n for duration, hodiaŭ simply tells you when something happens.

Naĝos is pronounced roughly like NAH-jos, where ĝ sounds like the j in jam.

Breakdown:

• na = like nah
• ĝ = English j sound
• os = like ose without a strong English diphthong

So naĝos is approximately NAH-jos.

A useful reminder:

• g = hard g as in go
• ĝ = j as in judge

A little, yes. Mi ne naĝos hodiaŭ is literally I will not swim today, which can sound like a clear decision or prediction.

In English, I’m not swimming today is often used for a planned near-future event. Esperanto usually just uses the normal future ending -os for that idea.

So even though English might prefer a present progressive form, Esperanto naturally says:

• Mi ne naĝos hodiaŭ.

That is not unusually strong; it is just standard Esperanto future usage.