La astronomo vidas ĉielkorpon.

Esperanto uses very regular word endings:

• -o marks a noun: astronomo = astronomer, ĉielkorpo = celestial body
• -as marks a present-tense verb: vidas = sees
• -n marks the direct object: ĉielkorpon = a celestial body, as the thing being seen

So the sentence breaks down like this:

• La astronomo = the astronomer
• vidas = sees
• ĉielkorpon = a celestial body

This kind of regular ending system is one of the main features of Esperanto.

La is the definite article, meaning the.

So:

• la astronomo = the astronomer
• ĉielkorpon without la = a celestial body or simply celestial body in an indefinite sense

Esperanto does not have a separate word for a/an. If a noun has no article, it is often understood as indefinite.

So:

• astronomo = an astronomer
• la astronomo = the astronomer

Likewise:

• ĉielkorpo = a celestial body
• la ĉielkorpo = the celestial body

The -n is the accusative ending. It marks the direct object, meaning the thing directly affected by the verb.

In this sentence:

• La astronomo is the one doing the seeing
• ĉielkorpon is the thing being seen

So -n tells you that ĉielkorpo is the object of vidas.

This is very useful because Esperanto can show sentence roles clearly even if the word order changes.

For example, these mean the same thing:

• La astronomo vidas ĉielkorpon.
• Ĉielkorpon vidas la astronomo.

The -n still tells you that ĉielkorpon is the object.

Usually, yes. The normal word order here is:

• subject
  • verb
    • object

So:

• La astronomo = subject
• vidas = verb
• ĉielkorpon = object

That matches English The astronomer sees a celestial body.

However, Esperanto has more freedom with word order than English because the -n ending helps show what the object is.

Still, for beginners, the most natural and easiest order is the same as in this sentence.

It is one word, and it is a compound noun.

It comes from:

• ĉielo = sky, heaven
• korpo = body

Together:

• ĉielkorpo = celestial body

Then the sentence adds -n because it is the direct object:

• ĉielkorpo
  • -n = ĉielkorpon

In Esperanto, compounds are very common. Usually the last part is the main idea, and the earlier part modifies it. So ĉielkorpo is literally something like sky-body.

A learner might expect that, because ĉiela means celestial or heavenly, and korpo means body.

So ĉiela korpo would be understandable. But ĉielkorpo is the standard compact term for celestial body.

Esperanto often prefers compounds for common ideas, especially in technical or scientific vocabulary.

So in this context, ĉielkorpo is the better choice.

The letter ĉ is pronounced like ch in church.

So:

• ĉielo starts with a ch sound
• ĉielkorpon also starts with that same ch sound

Stress in Esperanto is almost always on the second-to-last syllable of a word.

So:

• astronomo → as-tro-NO-mo
• vidas → VI-das
• ĉielkorpon → ĉi-el-KOR-pon

A rough pronunciation of the whole sentence is:

• la as-tro-NO-mo VI-das ĉi-el-KOR-pon

No. In Esperanto, verbs do not change for person or number.

So:

• mi vidas = I see
• vi vidas = you see
• li vidas = he sees
• ŝi vidas = she sees
• ili vidas = they see

The verb form vidas stays the same.

That is much simpler than English, where you have I see but he sees.

Vidas is present tense.

Esperanto tense endings are very regular:

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

So:

• vidas = sees / is seeing
• vidis = saw
• vidos = will see

This means once you learn the endings, you can recognize tense very quickly.

Yes. If you mean a specific celestial body, you could say:

• La astronomo vidas la ĉielkorpon.

That would mean The astronomer sees the celestial body.

Without la, as in the original sentence:

• La astronomo vidas ĉielkorpon.

the object is indefinite, so it means a celestial body.

So the original sentence has:

• a specific astronomer
• an unspecified celestial body

In Esperanto, plural nouns take -j.

So:

• astronomo = astronomer

• astronomoj = astronomers

• ĉielkorpo = celestial body
• ĉielkorpoj = celestial bodies

If a plural noun is also a direct object, it takes both -j and -n:

• ĉielkorpojn = celestial bodies, as a direct object

For example:

• La astronomo vidas ĉielkorpojn. = The astronomer sees celestial bodies.

This shows how Esperanto stacks endings in a very regular way.