Mia kuzino volas naĝi frue matene, kiam la strando ankoraŭ estas trankvila.

Because -ino is the feminine suffix in Esperanto.

• kuzo = cousin
• kuzino = female cousin

So Mia kuzino means my female cousin.

Because mia describes kuzino, which is the subject of the sentence.

In Esperanto, -n is used mainly for:

• the direct object
• motion toward something in some cases

Here, mia kuzino is the one doing the action, so it stays mia kuzino, not mian kuzinon.

After voli (to want), Esperanto normally uses an infinitive.

• volas = wants
• naĝi = to swim

So:

• Ŝi volas naĝi = She wants to swim

This works much like English wants to swim.

The ending -i marks the infinitive, the basic to ... form of a verb.

Examples:

• naĝi = to swim
• esti = to be
• voli = to want

So naĝi is not swims or swimming here; it is the basic verb form after volas.

ĝ is pronounced like the j in judge.

So naĝi sounds roughly like NAH-jee.

A few useful comparisons:

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

Both words add information about time.

• frue = early
• matene = in the morning

Together, frue matene means early in the morning.

This is a very natural Esperanto way to express time.
You could say just:

• frue = early
• matene = in the morning

But using both is more precise.

The ending -e makes an adverb.

• frua = early, early-related

• frue = early, in an early way

• matena = morning, morning-related
• matene = in the morning

So both frue and matene are adverbial expressions telling us when something happens.

Because kiam la strando ankoraŭ estas trankvila is a subordinate clause.

• kiam = when
• The part after it adds extra information about the time

Esperanto often uses commas to separate main clauses from subordinate clauses, especially when introduced by words like:

• kiam = when
• ĉar = because
• se = if
• ke = that

So the comma here is normal and helpful.

Kiam means when.

Here it introduces a time clause:

• kiam la strando ankoraŭ estas trankvila
• when the beach is still calm

It explains at what time she wants to swim: at the time when the beach is still calm.

La means the.

In this sentence, la strando refers to the beach being talked about in that situation, so it is treated as a specific beach:

• la strando = the beach

Esperanto uses la for definite nouns, much like English the.

Ankoraŭ means still.

So:

• la strando ankoraŭ estas trankvila = the beach is still calm

It suggests that later, the beach may become less calm, busier, noisier, or more active.

Because trankvila describes the noun strando.

• trankvila = calm, peaceful (adjective)
• trankvile = calmly, peacefully (adverb)

In the sentence:

• la strando estas trankvila = the beach is calm

The word after estas is describing the beach, so it must be an adjective: trankvila.

The ending -a marks an adjective.

Since trankvila describes strando, it must be an adjective, and adjectives in Esperanto end in -a.

Also, adjectives agree with the nouns they describe in number and case. Here:

• strando = singular, no -n
• so trankvila = singular, no -n

If the noun changed, the adjective would change too:

• la strando estas trankvila
• la strandoj estas trankvilaj

Not completely. Esperanto word order is fairly flexible, but some orders sound more natural than others.

The given sentence is very natural:

• Mia kuzino volas naĝi frue matene, kiam la strando ankoraŭ estas trankvila.

You could move some parts for emphasis, for example:

• Frue matene mia kuzino volas naĝi...

But the original order is clear and neutral.

In many contexts, yes, but they are not always identical in nuance.

• strando = shore, beach, strand
• plaĝo = beach, especially a bathing or recreational beach

In everyday modern use, many speakers use both for beach, but plaĝo often feels especially like a beach where people go to swim or relax.

So the original strando is fine, but plaĝo might also be possible depending on context.

A word-by-word breakdown is:

• Mia = my
• kuzino = female cousin
• volas = wants
• naĝi = to swim
• frue = early
• matene = in the morning
• kiam = when
• la = the
• strando = beach
• ankoraŭ = still
• estas = is
• trankvila = calm

So the structure is basically:

• My cousin wants to swim early in the morning, when the beach is still calm.

Because Esperanto does not use a separate word like English to before the infinitive. The infinitive ending -i already contains that meaning.

So:

• English: to swim
• Esperanto: naĝi

The -i does the job by itself.