La aĉetanto marĉandas kun la komercisto.

In Esperanto, la means the, and it does not change for gender, number, or case.

So:

• la aĉetanto = the buyer
• la komercisto = the merchant / the trader

It is used twice for the same reason English says the buyer and the merchant, not just one the for the whole sentence.

Aĉetanto is made from parts:

• aĉet- = buy
• -ant- = a person doing the action right now or in a general active sense
• -o = noun ending

So aĉetanto literally means one who is buying or buyer.

This is very typical Esperanto word-building. A learner often benefits from seeing that many words are constructed logically from smaller pieces.

This is a very common learner question.

• aĉetanto = buyer, the person who is buying in this situation
• aĉetisto would suggest someone whose role, profession, or habitual identity is connected with buying

In Esperanto:

• -ant- often describes someone performing the action
• -ist- often describes a profession, occupation, or habitual specialist

So in this sentence, aĉetanto is the natural choice because it means the person acting as the buyer in the transaction.

Marĉandas is the present-tense verb form.

It breaks down like this:

• marĉand- = bargain, haggle
• -as = present tense

So marĉandas means bargains, is bargaining, or haggles, depending on the context.

Esperanto present tense -as can cover what English expresses in several ways:

• bargains
• is bargaining
• sometimes even a general present sense like bargains habitually

Kun means with.

So:

• kun la komercisto = with the merchant

The sentence says the buyer is bargaining with the merchant, not doing something directly to the merchant.

That is why the sentence uses the preposition kun.

The -n ending usually marks the direct object in Esperanto.

But in this sentence, there is no direct object.

• La aĉetanto is the subject.
• marĉandas is the verb.
• kun la komercisto is a prepositional phrase.

Because la komercisto comes after the preposition kun, it does not take -n here.

So this is completely normal:

• kun la komercisto not
• kun la komerciston

Komercisto comes from:

• komerc- = trade, commerce
• -ist- = professional person, practitioner
• -o = noun

So komercisto means merchant, trader, or businessperson involved in trade.

It emphasizes that this person is connected with commerce as a role or profession.

They are similar, but not identical.

• komercisto = merchant, trader, someone involved in commerce
• vendisto = seller, vendor, salesperson

A vendisto focuses more directly on selling. A komercisto can sound a little broader, more like a trader or merchant.

Depending on context, either could be possible, but komercisto is perfectly natural if the idea is a merchant or trader.

A few pronunciation points matter here:

• ĉ is pronounced like ch in church
• every Esperanto letter has one regular sound
• stress falls on the second-to-last syllable

So roughly:

• aĉetanto → a-che-TAN-to
• marĉandas → mar-chan-DAS
• komercisto → ko-mer-CIS-to

Also:

• c in Esperanto sounds like ts as in cats
• so komercisto has that ts sound in ci

Esperanto word order is fairly flexible, but the most neutral order is:

• subject + verb + other elements

So:

• La aĉetanto marĉandas kun la komercisto.

is the most straightforward version.

Because Esperanto marks grammar clearly, other orders can be possible for emphasis, but they may sound less neutral to a beginner. For example, moving kun la komercisto earlier would give a different emphasis.

For learners, it is best to keep the normal order unless you have a reason not to.

Not necessarily.

You can bargain with someone, and the sentence can stop there if the context already makes clear what the bargaining is about.

So this sentence is complete even without naming the item or price.

If needed, Esperanto could add more information, such as what they are bargaining over, but it is not required for the sentence to be grammatical.

Possibly, depending on context, but marĉandi usually suggests bargaining, haggling, or negotiating over terms, especially price.

So the strongest everyday sense is closer to:

• bargain
• haggle

rather than a very broad or formal negotiate.

You would add -j for the plural.

Examples:

• La aĉetantoj marĉandas kun la komercisto. = The buyers are bargaining with the merchant.
• La aĉetanto marĉandas kun la komercistoj. = The buyer is bargaining with the merchants.
• La aĉetantoj marĉandas kun la komercistoj. = The buyers are bargaining with the merchants.

So:

• singular noun: -o
• plural noun: -oj

That same plural marker also affects adjectives if adjectives are present, but there are no adjectives in this sentence.