Si mercator pretium nimium poscit, pater nihil emit.

Si means if.

The sentence has two parts:

• Si mercator pretium nimium poscit = If the merchant asks too high a price
• pater nihil emit = the father buys nothing

This is a very common kind of Latin conditional: si + present tense, followed by another present tense. It often expresses a general idea, something like:

• If X happens, Y happens
• Whenever X happens, Y happens

So the sense is not necessarily about one single moment only; it can also describe a usual reaction.

Both mercator and pater are nominative singular, the case normally used for the subject of a verb.

• mercator = merchant
• pater = father

In this sentence:

• mercator is the subject of poscit
• pater is the subject of emit

So Latin is showing who does the action by case endings, not mainly by word order.

Pretium is accusative singular here, used as the direct object of poscit.

• poscit = asks for / demands
• pretium = price

So pretium poscit means he asks a price or more naturally in English, he asks too high a price / he demands too much.

Even though English may phrase this differently, Latin uses pretium as the thing being demanded.

Here nimium agrees with pretium and means too much / too high / excessive.

So:

• pretium nimium = too high a price / an excessive price

Because pretium is neuter singular accusative, nimium is also neuter singular accusative.

A learner might first think nimium is an adverb meaning too much, and sometimes it can be adverbial in Latin. But in this sentence it is most naturally understood as agreeing with pretium.

In Latin, adjective position is much freer than in English.

Both of these patterns are normal in Latin:

• adjective before noun
• adjective after noun

So pretium nimium is perfectly normal Latin word order. It does not mean anything very different from nimium pretium would mean.

Latin word order is often used for emphasis, rhythm, or style more than for basic grammar.

Poscit comes from poscere, which means to demand, to ask for, or to require.

So mercator pretium nimium poscit suggests not just a polite request, but that the merchant is asking or charging too much.

This is stronger than a very gentle asking. In context, it often implies something like:

• the merchant demands too high a price
• the merchant asks too much

Nihil means nothing and is the direct object of emit.

So:

• nihil emit = he buys nothing

For a beginner, the easiest way to understand it is simply: nihil is the thing bought, and that thing is nothing.

Latin often uses nihil where English could say either:

• he buys nothing
• he does not buy anything

Both are natural English translations.

Because those mean slightly different things.

• nihil emit = he buys nothing
• non emit = he does not buy

The first one includes an explicit object: nothing.
The second simply negates the verb and leaves the object unstated.

In many contexts the difference is small, but nihil emit is more specific.

Yes. Emit is the 3rd person singular present active indicative of emere.

So:

• emo = I buy
• emit = he/she buys

Here the subject is pater, so:

• pater emit = the father buys

Both poscit and emit are present tense because the sentence expresses a general present condition:

• If the merchant asks too much, the father buys nothing

This can mean:

• that is what happens now, or
• that is what usually happens in such a situation

Latin often uses the present tense in both parts of this kind of straightforward condition.

Yes. That is a very natural interpretation.

A Latin sentence with si and present tense can often express a repeated or general truth, not only a one-time event.

So depending on context, the sentence may mean either:

• If the merchant asks too high a price, the father buys nothing
• Whenever the merchant asks too high a price, the father buys nothing

Classical Latin does not have definite or indefinite articles like English the or a/an.

So:

• mercator can mean merchant, a merchant, or the merchant
• pater can mean father, a father, or the father

The context tells you which is most natural in translation.

That is why a single Latin sentence can be translated in slightly different ways in English without changing the basic meaning.

We know mainly from case endings and verb endings, not just from position.

In this sentence:

• mercator is nominative, so it fits as the subject of poscit
• pretium is accusative, so it fits as the object of poscit
• pater is nominative, so it fits as the subject of emit
• nihil is the object of emit

Latin word order is flexible because the endings carry much of the grammatical information.

Not really in the same way it is in modern printed English.

The comma here simply helps the reader see the two parts of the sentence:

• the if-clause
• the main clause

In modern editions and textbooks, punctuation is added for clarity. But the grammar of the sentence does not depend on the comma.