Mater a bibliopola Graeco duo volumina mercatur: unum Latine scriptum, alterum Graece.

Because mercatur is from mercor, mercari, mercatus sum, a deponent verb. Deponent verbs use passive-looking forms but have active meanings.

So:

• mercatur = he/she buys, trades, or deals
• here it means she buys

This is one of the first things English-speaking learners often notice, because in English a form like this would usually look passive, but in Latin it is not passive at all.

mercatur is:

• 3rd person singular
• present tense
• indicative mood
• from the deponent verb mercor

So it means she is buying / she buys.

It matches Mater, which is singular.

Because the preposition a/ab takes the ablative case.

Here a bibliopola Graeco means from a Greek bookseller.

So:

• a = from
• bibliopola = ablative singular
• Graeco = ablative singular, agreeing with bibliopola

This is a common pattern in Latin: a preposition determines the case of the noun that follows it.

Here it means from.

The preposition a/ab can mean:

• from, especially with people or places
• by, especially with the agent in a passive sentence

In this sentence, since Mater is actively buying something, a bibliopola Graeco tells you the source of the books, not the doer of a passive action. So from a Greek bookseller is the right sense.

Because some Latin nouns referring to male professions or roles belong to the first declension even though they are masculine.

bibliopola, bibliopolae means bookseller and is masculine despite its first-declension ending.

This can feel strange to English speakers, and even to learners who associate:

• first declension = feminine

But that is only a common pattern, not an absolute rule. Other masculine first-declension nouns include words like poeta and agricola.

Because Graeco must agree with bibliopola, and bibliopola is in the ablative singular after a.

So:

• nominative: bibliopola Graecus
• ablative after a: a bibliopola Graeco

Even though Graecum might feel tempting if you are thinking of the dictionary form, Latin adjectives must match their nouns in:

• gender
• number
• case

It simply uses a different noun here.

volumen, voluminis is a neuter third-declension noun meaning volume, scroll, or sometimes book depending on context.

So:

• duo volumina = two volumes / two books

Latin could also use liber for a book, but this sentence happens to use volumina.

Also notice that because volumina is neuter plural, the numeral must be the neuter plural form duo, not masculine duos or feminine duae.

They are in the accusative plural, because they are the direct object of mercatur.

The mother is buying two volumes, so those words answer what is she buying?

For this noun:

• nominative singular: volumen
• accusative singular: volumen
• nominative plural: volumina
• accusative plural: volumina

Since neuter plural nominative and accusative are the same, volumina could be either form in another sentence, but here the meaning and syntax show it is accusative.

Because volumen is a neuter noun.

Its adjective and numeral forms must therefore match that gender. That is why we get:

• duo volumina
• unum
• alterum
• scriptum

All of those are neuter singular or plural forms agreeing with the implied noun volumen.

They are neuter because they refer to volumen, which is neuter.

The sentence breaks down the two volumes like this:

• unum Latine scriptum = one written in Latin
• alterum Graece = the other in Greek

Both unum and alterum stand for one volume and the other volume, so they must be neuter singular accusative to match the understood noun.

unum means one, and alterum means the other.

Latin often uses alter when there are two things and you want to distinguish the second from the first:

• unum ... alterum ... = one ... the other ...

This is more natural in Latin than simply repeating unum twice.

Because it agrees with the understood noun volumen.

In unum Latine scriptum, the word scriptum is a participle meaning written, and it must agree with what it describes:

• unum = one volume
• scriptum = written

Since volumen is neuter singular here, scriptum is also neuter singular.

scriptum is the perfect passive participle of scribo, scribere.

It means written.

So Latine scriptum means written in Latin.

English speakers often find this easy to recognize once they know the participle system, because it works similarly to English written, though Latin uses agreement much more visibly.

Because Latin often leaves out a word that is easily understood from the previous phrase. This is called ellipsis.

So:

• unum Latine scriptum
• alterum Graece

really means:

• unum Latine scriptum
• alterum Graece scriptum

Latin does this very naturally when the missing word is obvious.

Because they mean in Latin and in Greek, expressing the language in which something is written.

These are adverbs formed from adjectives:

• Latine = in Latin
• Graece = in Greek

So:

• Latine scriptum = written in Latin
• Graece scriptum = written in Greek

English often uses a prepositional phrase, but Latin commonly uses an adverb for the language.

Not here, if the meaning is in Latin and in Greek.

Those would be adjective forms, not adverbs. The sentence needs adverbs because it is describing how or in what language the books are written.

So the correct forms here are:

• Latine
• Graece

not adjective forms agreeing with volumen.

Because Latin word order is much more flexible than English word order, since Latin uses case endings to show grammatical function.

English relies heavily on position:

• Mother buys two books

Latin can move parts around more freely because the endings already show what each word is doing.

In this sentence, the order helps highlight information neatly:

• Mater = subject first
• a bibliopola Graeco = source
• duo volumina = object
• mercatur = verb at the end
• then the colon gives extra detail about the two volumes

This kind of arrangement is very normal in Latin prose.

The colon introduces an explanation or breakdown of the two volumes.

First the sentence says that the mother buys two volumes. Then after the colon it specifies them individually:

• unum Latine scriptum
• alterum Graece

So the colon works much like namely or that is to say in English.

Latin has no articles like English the or a/an.

So Mater can mean:

• mother
• the mother
• a mother

The correct English choice depends on context. In many textbook sentences, Mater is naturally translated as Mother or the mother.

Because once the noun has already been stated, Latin often avoids repeating it unnecessarily.

After duo volumina, it is perfectly clear that:

• unum = one volume
• alterum = the other volume

English can do this too: She bought two books, one in Latin, the other in Greek.

So this structure is economical and very natural.

It describes the bookseller.

This is clear from agreement:

• bibliopola = ablative singular
• Graeco = ablative singular masculine

So Graeco matches bibliopola, not volumina.

If it described the books, it would have to agree with volumina, which is neuter plural, and the form would be different.

Yes. The verb mercor can have a broader commercial sense such as trade, deal in, or purchase.

But in this sentence, with a person obtaining books from a bookseller, buys is the most natural translation.

So a learner should know the wider meaning of the verb, but also recognize that context narrows it here.