Aliqui in bibliotheca tacent, alii de auctore disputant.

Aliqui means some or some people, and alii means others.

In this sentence, both words are being used substantively—that is, they stand on their own without a noun like homines (people) being stated. Latin often does this when the noun is easy to understand.

So the sentence is basically:

• Aliqui = some people
• alii = other people / others

They are both masculine plural nominative here, because they are the subjects of the two verbs.

They are plural because the sentence is talking about more than one person in each group:

• some people are silent
• other people are discussing the author

Latin marks this clearly with both the subject words and the verb endings:

• aliqui ... tacent = some people are silent
• alii ... disputant = others are discussing

The verb endings -ent and -ant also show third person plural.

Because in can take either the ablative or the accusative, depending on the meaning.

• in + ablative = in / on a place, showing location
• in + accusative = into / onto a place, showing motion toward

Here, in bibliotheca means in the library, so it expresses location. That is why bibliotheca is in the ablative singular.

Compare:

• in bibliotheca tacent = they are silent in the library
• in bibliothecam intrant = they enter into the library

Bibliotheca is ablative singular here.

You can tell mainly because of the preposition in, which with a meaning of location takes the ablative. Also, bibliotheca is a first-declension noun, and its ablative singular ending is -a.

So:

• nominative singular: bibliotheca = the library
• ablative singular: bibliotheca = in/by/with/from the library, depending on context

The form looks the same as the nominative singular, but the preposition in tells you its function here.

Because the preposition de takes the ablative case.

So:

• de = about / concerning
• auctore = ablative singular of auctor

Together, de auctore means about the author.

This is a very common Latin pattern:

• de amico = about the friend
• de bello = about the war
• de urbe = about the city

Auctore is the ablative singular of auctor, which means author.

Auctor is a third-declension noun. Its basic forms are:

• nominative singular: auctor
• genitive singular: auctoris
• ablative singular: auctore

Since it follows de, it has to be ablative: de auctore.

Both are present active indicative, third person plural.

• tacent = they are silent / they keep silent
• disputant = they discuss / they are discussing

The ending -nt is the key sign of third person plural in the present tense.

More specifically:

• tacent comes from tacere (to be silent / keep silent), a 2nd-conjugation verb
• disputant comes from disputare (to discuss / argue / debate), a 1st-conjugation verb

Because Latin usually does not need an explicit subject pronoun when the verb ending already shows the person and number.

Here:

• tacent already means they are silent
• disputant already means they discuss

The subject is made even clearer by aliqui and alii, so adding a separate word for they would be unnecessary.

This is very normal in Latin. English usually needs a subject pronoun, but Latin often does not.

Latin word order is much more flexible than English word order because the endings show the grammatical relationships.

This sentence follows a very natural Latin pattern:

• subject
• prepositional phrase
• verb

So:

• Aliqui = subject
• in bibliotheca = where
• tacent = verb

and then again:

• alii = subject
• de auctore = about what
• disputant = verb

Putting the verbs tacent and disputant at the end is especially common in Latin. It gives the sentence a balanced structure.

Yes. They form a nice contrast:

• aliqui = some
• alii = others

Latin often uses pairs like this to divide a group into parts. English does the same with some ... others ....

So the sentence sets up two different groups of people in the library:

• one group is silent
• another group is discussing the author

This contrast is one of the main ideas of the sentence.

It can suggest both ideas.

The verb tacere basically means to be silent or to keep silent. In context, that may imply:

• they are quiet
• they are saying nothing
• they are not speaking

So tacent is slightly broader than a mechanical English translation like are silent. It describes a state of silence, often with the sense that the people are refraining from speaking.

It can mean either, depending on context.

The verb disputare often means:

• to discuss
• to debate
• to argue

So de auctore disputant could mean:

• they are discussing the author
• they are debating the author
• they are arguing about the author

If the meaning has already been given to the learner, that translation should guide the exact nuance. Grammatically, though, the Latin itself allows a range from discussion to debate.

Yes, it could have, but Latin often leaves such nouns out when they are obvious.

For example, a fuller version might be something like:

• Aliqui homines in bibliotheca tacent, alii homines de auctore disputant.

But this would sound more repetitive than necessary. Since aliqui and alii already clearly mean some people and others, Latin normally omits the noun.

This is very common and natural.