La insekto mortis apud la fenestro.

In Esperanto, -o is the standard noun ending. So insekto means insect as a noun.

A few related patterns:

• insekto = insect
• insektoj = insects
• insekta = insect-related / insectlike (adjective)

This is one of the most regular parts of Esperanto: if you see -o, you are usually looking at a noun.

Because morti means to die, and it is an intransitive verb. That means it does not take a direct object.

So:

• La insekto mortis. = The insect died.

But you do not say that the insect died something.

Compare:

• mortigi = to kill, to cause to die

So:

• La insekto mortis. = The insect died.
• Li mortigis la insekton. = He killed the insect.

-is is the Esperanto ending for the past tense.

So:

• morti = to die
• morta = dead (adjective, different word form)
• mortas = dies / is dying
• mortis = died
• mortiĝos? Not here; but mortos = will die

In your sentence, mortis tells you the action happened in the past: died.

La is Esperanto’s definite article, meaning the.

So:

• la insekto = the insect
• la fenestro = the window

Esperanto has only one definite article: la. It does not change for gender, number, or case in the basic form.

A native English speaker might wonder whether both uses are necessary. In Esperanto, if both nouns are definite in meaning, using la before both is completely normal.

Apud means beside, next to, by, or close to.

So:

• apud la fenestro = beside the window / by the window

It usually suggests physical nearness.

A useful comparison:

• ĉe = at, with, in the vicinity of
• apud = specifically beside/next to

So apud la fenestro gives a clearer image of the insect dying near or beside the window.

Because there is no direct object here.

The accusative ending -n is often used for a direct object:

• Mi vidas la insekton. = I see the insect.

But in La insekto mortis apud la fenestro, nothing is being directly acted on by the verb mortis. The insect is the subject, and apud la fenestro is a prepositional phrase.

Also, apud normally takes a noun without -n:

• apud la fenestro = beside the window

So no accusative is needed in this sentence.

Yes. Esperanto word order is fairly flexible because the grammar endings do a lot of the work.

The most neutral order is:

• La insekto mortis apud la fenestro.

But you could also say:

• Apud la fenestro mortis la insekto.

That still means the same thing, though it may sound more literary or place extra focus on apud la fenestro.

For learners, the original version is the clearest and most natural starting point.

For the same reason as insekto: it is a noun.

• fenestro = window
• fenestroj = windows
• fenestra = window-related

Esperanto uses the same noun ending -o very consistently, which makes vocabulary easier to recognize.

A simple pronunciation guide is:

La insekto mortis apud la fenestro.
lah in-SEK-to MOR-tis ah-POOD lah feh-NES-tro

A few pronunciation notes:

• c is always like ts
• e is like e in met
• o is a clear o
• stress is usually on the second-to-last syllable

So:

• in-SEK-to
• MOR-tis
• a-PUD
• fe-NES-tro

Yes, both are reasonable translations depending on context.

Apud usually means something like:

• by
• beside
• next to
• near

If you want the most literal and spatially clear translation, beside the window or next to the window is especially good.

If the meaning shown to the learner uses by the window, that is also perfectly natural English.

Yes. It is already a complete sentence:

• La insekto = the insect
• mortis = died

So:

• La insekto mortis. = The insect died.

The phrase apud la fenestro simply adds extra information about location:

• where it died

That makes the full sentence more specific, but the core sentence is already complete without it.