Magistra discipulos monet ne in palaestra nimis celeriter currant.

Magistra is in the nominative singular, which is the case normally used for the subject of a finite verb in Latin. The verb monet is also third person singular, so it matches a singular subject: the teacher warns.

The ending -a here does not automatically mean accusative or anything else; for a first-declension noun like magistra, -a is the nominative singular ending.

Because discipulos is the direct object of monet. The teacher is warning the students, so the students are the ones receiving the action of the verb.

• discipuli = nominative plural, the students as subject
• discipulos = accusative plural, the students as object

So Latin marks the object with the accusative ending -os.

Monet comes from moneo, monere, meaning to warn, advise, remind, or caution, depending on context.

In this sentence it introduces a warning or instruction. A very common Latin pattern is:

moneo / impero / persuadeo / rogo + person + clause

Here that pattern is:

• magistra = the teacher
• discipulos = the students
• monet = warns
• ne ... currant = not to run ...

So monet is doing more than just standing alone; it introduces what the students are being warned not to do.

Because ne is the normal word used to introduce a negative command, warning, or purpose-type clause in Latin.

Here the sentence is not simply saying the students do not run. Instead, it is saying that the teacher warns them not to run. That kind of idea uses ne.

So:

• non currunt = they do not run
• monet ne currant = she warns them not to run

A native English speaker often wants to use non everywhere for not, but Latin distinguishes between simple negation and the kind of clause introduced by verbs of warning or command.

Because after monet with ne, Latin uses a subjunctive clause. This is often called an indirect command or, with verbs of warning, a closely related construction.

So:

• currunt = indicative, they run
• currant = subjunctive, used in a dependent clause such as that they run or that they not run

In this sentence, ne ... currant means that they not run or more naturally in English, not to run.

This is one of the most important patterns to learn:

• imperat ut veniant = he orders them to come
• monet ne currant = she warns them not to run

It is best understood as an indirect command after a verb of warning, or more specifically as a substantive clause of fearing/warning-like force depending on how a textbook labels it. In most beginner and intermediate courses, the simplest and most useful label is:

verb of warning + ne + subjunctive = warns someone not to do something

So in practical terms, you should recognize the whole unit:

discipulos monet ne ... currant
= she warns the students not to run ...

The important thing is the pattern, even if different grammar books give slightly different names to it.

Because in takes different cases depending on whether it means in/on or into.

• in
  • ablative = location, in or on
• in
  • accusative = motion toward, into

Here the students are running in the gymnasium / in the exercise ground, meaning within that place, so Latin uses the ablative:

• in palaestra = in the gym
• in palaestram would suggest into the gym

So the sentence is about where they are running, not where they are going.

Palaestra is a feminine noun meaning a wrestling school, exercise ground, or gymnasium in the ancient world.

In this sentence it is in the ablative singular after in, so in palaestra means in the exercise ground / in the gym.

For an English-speaking learner, it is worth noting that this is not exactly a modern school gym in every context; it refers to a classical place for athletic exercise.

They do, but they do different jobs.

• celeriter = quickly
• nimis = too, excessively

So:

• currant celeriter = they run quickly
• currant nimis celeriter = they run too quickly

In other words, celeriter tells how they run, and nimis modifies celeriter to show degree.

Celeriter is the adverb from celer, celeris, celere, meaning quick. The adverb means quickly.

A common way to form adverbs from third-declension adjectives is with -iter or -ter, so:

• celer = quick
• celeriter = quickly

Since it modifies the verb currant, it needs to be an adverb, not an adjective. Latin is doing exactly what English does in quickly run rather than quick run.

Yes, Latin could vary the word order much more freely than English, because the endings show the grammatical roles.

This sentence is quite natural as written:

Magistra discipulos monet ne in palaestra nimis celeriter currant.

But Latin could rearrange parts for emphasis, for example:

• Discipulos magistra monet ne in palaestra nimis celeriter currant.
• Ne in palaestra nimis celeriter currant, discipulos magistra monet.

The basic relationships stay clear because of the endings:

• magistra = nominative subject
• discipulos = accusative object
• currant = plural subjunctive verb

So word order in Latin often affects emphasis more than basic grammar.

There are two clues.

First, currant is third person plural, so it needs a plural subject in sense. The nearest logical plural idea is discipulos, the students.

Second, the pattern monet aliquem ne... means warns someone not to..., so the people being warned are understood as the ones who would do the action in the subordinate clause.

So Latin does not need to repeat they. It is understood from the construction:

magistra discipulos monet ne ... currant
= the teacher warns the students not to run ...

No. With this kind of negative clause after a verb of warning, Latin normally uses ne directly.

So the sentence is:

monet ne currant

not:

monet ut ne currant

In English we often say warns them not to run, and Latin expresses that directly with ne + subjunctive. There is no need for an extra ut here.