La substrato estas malseka.

In Esperanto, -o marks a noun. So substrato is a noun meaning substrate or growing medium, depending on context.

This is one of the most basic Esperanto endings:

• -o = noun
• -a = adjective
• -e = adverb
• -i = infinitive verb

So the sentence structure is easy to recognize:

• La substrato = the substrate
• estas = is
• malseka = wet/damp

Because malseka is an adjective, and Esperanto adjectives end in -a.

It describes the noun substrato, so it has to be in adjective form:

• seka = dry
• malseka = wet, damp

In this sentence, malseka is a predicate adjective after estas, just like wet in English The substrate is wet.

Because the word is describing a noun, not a verb.

• malseka = wet, damp → adjective
• malseke = wetly, damply → adverb

Here, the sentence says what the substrate is, so you need an adjective:

• La substrato estas malseka. = The substrate is wet.

If you used malseke, it would be grammatically wrong in this sentence.

Estas means is / am / are, depending on the subject. It is the present-tense form of esti = to be.

Examples:

• mi estas = I am
• vi estas = you are
• li estas = he is
• la substrato estas = the substrate is

Esperanto uses the same present-tense verb form for all subjects, which makes it much simpler than English.

La is the definite article, meaning the.

So:

• substrato = substrate
• la substrato = the substrate

Esperanto has only one definite article, la, and it does not change for gender, number, or case in normal use.

Yes, but it changes the meaning slightly.

• La substrato estas malseka. = The substrate is wet.
• Substrato estas malseka. = Substrate is wet or a substrate is wet, which sounds less natural unless you are speaking very generally.

If you are talking about a specific substrate that both speaker and listener know, la is the normal choice.

Because there is no direct object.

The sentence has:

• a subject: la substrato
• a linking verb: estas
• a predicate adjective: malseka

The accusative -n is usually used for a direct object, but here nothing is being acted upon. The sentence is just describing the subject.

So:

• La substrato estas malseka. = correct
• La substraton estas malseka. = wrong
• La substrato estas malsekan. = wrong

Actually, it does match substrato.

In Esperanto, adjectives agree with the nouns they describe in:

• number
• accusative case

Here, substrato is:

• singular
• not accusative

So the adjective stays in its basic form:

• substrato → singular
• malseka → singular adjective

If the noun were plural, you would say:

• La substratoj estas malsekaj. = The substrates are wet.

If it were accusative in another sentence, the adjective would also take -n.

It is built from parts, and that is very typical of Esperanto.

• sek- = dry
• -a = adjective ending
  So seka = dry

Then Esperanto adds:

• mal- = opposite

So:

• seka = dry
• malseka = wet, damp

This is a very common and useful pattern in Esperanto:

• bona = good → malbona = bad
• varma = warm → malvarma = cold
• fermi = to close → malfermi = to open

Usually it means wet or damp, but the exact nuance depends on context.

In many situations, malseka can mean:

• damp
• moist
• wet

So La substrato estas malseka could refer to soil, potting mix, or some other medium being moist enough to feel wet.

English often distinguishes more sharply between damp, moist, and wet, but Esperanto malseka can cover a range of similar meanings.

A simple pronunciation guide is:

la sub-stra-TO ES-tas mal-SE-ka

A few helpful points:

• Stress in Esperanto is always on the second-to-last syllable.
• So:
  • substrato → sub-stra-TO
  • estas → ES-tas
  • malseka → mal-SE-ka

Approximate sounds:

• a like a in father
• e like e in bet
• o like o in for (without an English glide)

The normal word order here is very natural:

• La substrato estas malseka.

But Esperanto word order is fairly flexible, especially in simple sentences like this. For emphasis, you could also say:

• Malseka estas la substrato.

That sounds more marked, like Wet is the substrate or The substrate is wet with emphasis on wet.

For learners, the standard order subject + verb + adjective is the best choice.

It is basically an international/scientific word that Esperanto uses in a regular way.

That is common in Esperanto, especially for technical vocabulary. A word like substrato is easy to recognize if you know English or another European language with similar scientific terms.

Even borrowed words follow Esperanto grammar normally:

• substrato = noun
• substrata = adjectival form if needed
• substratoj = plural

So it may be international in origin, but it behaves like any ordinary Esperanto word.