Magistra eos monet ut in bibliotheca taceant.

Because magistra is in the nominative singular, which is the case typically used for the subject.

• magistra = the female teacher
• The verb monet is also third person singular, so it matches a single subject.

So magistra monet means the teacher warns/advises.

eos means them.

It is the masculine accusative plural form of the pronoun is, ea, id. It is accusative because it is the direct object of monet:

• magistra = the teacher
• eos = them
• monet = warns/advises

So the teacher is warning them.

A learner might expect they, but Latin uses the accusative here because English warn someone also takes a direct object.

Because the subject is one teacher, not several.

• monet = she warns / the teacher warns (third person singular)
• monent = they warn (third person plural)

Since magistra is singular, the verb must also be singular.

Here ut introduces a clause of command or urging after a verb like moneo.

So the structure is:

• magistra eos monet = the teacher warns/advises them
• ut ... taceant = to be quiet / that they should be quiet

Latin often uses:

• a verb of ordering, advising, persuading, warning, etc.
• followed by ut
• followed by a subjunctive verb

This is different from English, which often uses an infinitive: The teacher warns them to be quiet.

Because after ut in this kind of clause, Latin uses the subjunctive.

• tacent = they are silent / they are being quiet (indicative, plain statement)
• taceant = that they be quiet / that they should be quiet (present subjunctive)

This is not just saying what they are doing; it expresses what the teacher wants or tells them to do.

So ut ... taceant means something like:

• that they should be quiet
• to be quiet

Because the understood subject of taceant is eos = them, which is plural.

• taceat = that he/she/it be quiet (singular)
• taceant = that they be quiet (plural)

Even though eos is not repeated inside the ut clause, it is understood as the subject there.

Because in with the ablative usually means in or inside a place.

• in bibliotheca = in the library

This expresses location, not motion.

Compare:

• in bibliotheca = in the library (where?)
• in bibliothecam = into the library (where to?)

Since the sentence is about being quiet in the library, the ablative is correct.

bibliotheca is ablative singular.

It is ablative because it follows in in the sense of location:

• in + ablative = in/on a place
• in + accusative = into/onto a place

So in bibliotheca means in the library, not into the library.

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

For example, these would mean essentially the same thing:

• Magistra eos monet ut in bibliotheca taceant.
• Eos magistra monet ut in bibliotheca taceant.
• Ut in bibliotheca taceant, magistra eos monet.

However, the usual word order can affect emphasis.

In the given sentence:

• Magistra comes first, so the teacher is introduced clearly.
• eos comes early, so we quickly see whom she is addressing.
• taceant comes at the end of the clause, which is very normal in Latin.

It depends on context.

The verb moneo, monere can mean:

• warn
• advise
• remind
• sometimes urge

In this sentence, since the teacher wants them to be quiet, English might naturally say:

• The teacher warns them to be quiet
• The teacher tells/advises them to be quiet

If the meaning has already been given to the learner, the important grammar point is that moneo can take a person plus an ut clause.

Because after verbs like moneo, Latin often prefers a full subordinate clause with ut + subjunctive rather than an English-style infinitive.

English says:

• The teacher advises them to be quiet.

Latin says:

• Magistra eos monet ut ... taceant.
• literally, The teacher advises them that they should be quiet.

So this is a normal Latin construction, even though English expresses it differently.

Yes. Magistra is the feminine form.

• magister = male teacher/master
• magistra = female teacher/mistress/teacher

So the sentence specifically tells you that the teacher is female.

The people meant to be quiet are eos = them.

In Latin, the subject of the ut clause is often understood from the main clause. Here:

• magistra warns eos
• ut ... taceant = that they should be quiet

So the implied subject of taceant is the same group referred to by eos.

Yes. This is commonly called an indirect command or substantive clause of command.

The pattern is:

• verb of commanding/advising/warning/persuading
• ut (or sometimes ne for a negative command)
• subjunctive

So:

• monet ut taceant = advises/warns that they should be quiet

This is an important Latin construction to recognize.