Stampo estas sur la naskiĝatesto.

Because stampo is being used in an indefinite sense: a stamp, not the stamp.

In Esperanto:

• stampo = a stamp or just stamp
• la stampo = the stamp

So Stampo estas sur la naskiĝatesto means something like A stamp is on the birth certificate. If you said La stampo estas sur la naskiĝatesto, that would mean The stamp is on the birth certificate, referring to a specific stamp already known from context.

Estas is the present tense of esti, which means to be.

So:

• esti = to be
• estas = is / are / am

In this sentence, estas links the subject stampo with the location phrase sur la naskiĝatesto.

So the structure is:

• Stampo = a stamp
• estas = is
• sur la naskiĝatesto = on the birth certificate

Sur means on, usually in the sense of being on a surface or attached to something.

Examples:

• sur la tablo = on the table
• sur la muro = on the wall
• sur la naskiĝatesto = on the birth certificate

So here it shows location.

La means the. It is used when the speaker has a specific thing in mind.

So:

• naskiĝatesto = a birth certificate / birth certificate
• la naskiĝatesto = the birth certificate

In many real situations, a document like this is a specific known document, so la is natural.

Also, Esperanto uses la a lot like English the, though sometimes usage does not match English exactly. Here it works very naturally as the birth certificate.

It is a compound word made from smaller parts:

• naskiĝi = to be born
• naskiĝo = birth
• atesto = attestation, certificate, official confirmation

So naskiĝatesto literally means something like birth certificate or certificate of birth.

This is very common in Esperanto: long words are often built from clear pieces.

The -n ending usually marks the direct object, and it can also show direction toward somewhere.

But in this sentence:

• Stampo is the subject
• sur la naskiĝatesto is a location, not a direction and not a direct object

So no accusative is needed.

Compare:

• Stampo estas sur la naskiĝatesto. = A stamp is on the birth certificate.

  • location only, so no -n

• Mi metas stampon sur la naskiĝateston. = I put a stamp onto the birth certificate.

  • stampon gets -n because it is the direct object
  • naskiĝateston can take -n because the phrase shows movement onto the certificate

Yes. Esperanto word order is fairly flexible, especially in simple sentences like this.

These are all possible, though they may differ slightly in emphasis:

• Stampo estas sur la naskiĝatesto.
• Sur la naskiĝatesto estas stampo.

The second version puts more attention on the location first, as if answering What is on the birth certificate?

The version you were given is straightforward and easy for learners:

• subject first
• verb second
• location after that

Yes, that is also possible.

It has a slightly different feel:

• Stampo estas sur la naskiĝatesto = a stamp is on the birth certificate
• Estas stampo sur la naskiĝatesto = there is a stamp on the birth certificate

Esperanto does not need a separate word like English there in there is. Often estas alone can do that job.

So both are grammatical, but the focus is a bit different.

A helpful breakdown is:

• nas-ki-ĝa-tes-to

The letter ĝ is pronounced like the g in gem or judge.

So naskiĝatesto sounds roughly like:

• nahs-kee-jah-teh-stoh

A few pronunciation tips:

• a = like a in father
• e = like e in met
• o = like o in for, but usually cleaner and shorter
• stress in Esperanto usually falls on the second-to-last syllable

So in naskiĝatesto, the stress is on tes:

• nas-ki-ĝa-TES-to

It can mean either, depending on context.

Stampo is a general word for a stamp or stamping mark. In a sentence about a document like a birth certificate, many learners will naturally understand it as an official stamp, seal, or stamp mark rather than a postage stamp.

If you need to be more specific, context or extra words can help:

• poŝtmarko = postage stamp
• oficiala stampo = official stamp
• sigelo = seal, especially an official or formal seal

So in this sentence, stampo most likely means an official stamp on the document.