Ĉi tiu spico estas bona.

In Esperanto, nouns normally end in -o. So spico is a noun.

This makes word classes very easy to recognize:

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

So when you see spico, you can immediately tell it is a noun.

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

So:

• bona = good
• granda = big
• varma = warm

In this sentence, bona describes spico, so it uses the adjective ending -a.

Adjectives in Esperanto agree with the nouns they describe.

Here, spico is:

• singular
• not accusative

So the adjective is also:

• singular
• not accusative

That gives bona.

If the noun were plural, you would also make the adjective plural:

• Ĉi tiuj spicoj estas bonaj. = These spices are good.

If the noun were accusative, the adjective would also take -n:

• Mi aĉetas ĉi tiun bonan spicon. = I am buying this good spice.

Ĉi tiu is a demonstrative expression meaning this.

The core word is tiu, which means that one / that. Adding ĉi makes it mean this instead of that.

So:

• tiu spico = that spice
• ĉi tiu spico = this spice

It works like a determiner before the noun.

Yes. Ĉi tiu spico and tiu ĉi spico are both correct.

They mean the same thing. In modern usage, ĉi tiu is often more common, but both are standard Esperanto.

So you may see:

• ĉi tiu spico
• tiu ĉi spico

Both mean this spice.

Esperanto verbs do not change according to person or number.

So esti = to be becomes:

• mi estas = I am
• vi estas = you are
• li estas = he is
• ili estas = they are

The form estas always marks present tense. It does not change for singular/plural or for different subjects.

That is why spico being singular does not affect the form of the verb.

Because nothing in this sentence is in the accusative.

The subject is ĉi tiu spico, and after estas you have a predicate adjective, bona. Predicate adjectives after esti do not take the accusative.

So:

• Ĉi tiu spico estas bona. = correct

But if the noun were a direct object, you would use -n:

• Mi ŝatas ĉi tiun spicon. = I like this spice.

Here:

• ĉi tiu spico is the subject
• bona describes the subject through estas

So no accusative ending is needed.

Esperanto has no indefinite article like English a or an.

So a bare noun can often correspond to English a, an, or just the noun by itself, depending on context.

Examples:

• spico = spice / a spice
• bona spico = a good spice / good spice

Esperanto does have a definite article, la, for the, but it is not used here because the sentence uses ĉi tiu, which already makes the noun definite and specific.

Yes, Esperanto word order is fairly flexible, though the most neutral order here is:

Ĉi tiu spico estas bona.

You could also say:

• Bona estas ĉi tiu spico.

That is grammatically possible, but it sounds more marked or stylistic, as if emphasizing bona.

For normal everyday use, the original order is the clearest and most natural.

A native English speaker often especially wonders about ĉ.

A simple guide:

• ĉ sounds like ch in church
• c sounds like ts in cats
• sp is pronounced as written
• stress is on the second-to-last syllable of each word

So approximately:

• ĉi ≈ chee
• tiu ≈ TEE-oo
• spico ≈ spi-TSO
• estas ≈ ES-tas
• bona ≈ BO-na

Stress:

• ĈI tiu is a one-syllable word plus a two-syllable word, so TI in tiu is stressed
• spi-co → stress on SPI
• es-tas → stress on ES
• bo-na → stress on BO

To make it plural, both the noun and the adjective take -j, and ĉi tiu becomes ĉi tiuj.

So:

• Ĉi tiu spico estas bona. = This spice is good.
• Ĉi tiuj spicoj estas bonaj. = These spices are good.

Notice:

• spico → spicoj
• bona → bonaj
• ĉi tiu → ĉi tiuj

The verb stays the same:

• estas in both singular and plural.