Haec via prorsus tuta non est nocte; magistra tamen plane ostendit cur discipuli nunc intro maneant.

Because via is feminine, singular, nominative, and haec has to agree with it.

• via = a road, way
• It is a first-declension feminine noun
• So the demonstrative must also be feminine singular nominative

That gives:

• haec via = this road

The adjective also agrees:

• tuta = safe
  So haec via ... tuta means this road ... safe.

Yes. Latin word order is much freer than English word order.

Here:

• tuta = safe
• non est = is not

So prorsus tuta non est means is not completely safe.

Latin often places words for emphasis rather than because of a fixed subject-verb-object pattern. You could see other orders such as:

• haec via non est prorsus tuta
• haec via tuta prorsus non est

They would mean roughly the same thing, though the emphasis may shift slightly.

Prorsus is an adverb meaning completely, altogether, or absolutely.

So:

• prorsus tuta non est = is not at all safe / is not completely safe

It strengthens the statement. It is not just saying the road is unsafe; it is stressing the point.

Because Latin often uses the ablative of time when without a preposition.

• nocte = at night

This is a very common Latin construction for time expressions:

• die = by day / in the daytime
• aestate = in summer
• prima luce = at dawn

So non est nocte means is not safe at night, with nocte in the ablative.

Tamen usually means however, nevertheless, or still.

Here it marks a contrast between the two clauses:

• the road is not safe at night;
• however, the teacher clearly explains why the students should stay inside now.

So tamen helps connect the ideas: despite the danger just mentioned, the teacher is giving an explanation.

Plane is an adverb meaning clearly, plainly, or openly.

So:

• plane ostendit = she shows clearly / explains plainly

It is not exactly the same as prorsus.

• prorsus = completely, absolutely
• plane = clearly, plainly

Both are adverbs, but they describe different kinds of emphasis.

Yes, Latin often leaves the subject unstated when the verb already shows the person and number.

• ostendit by itself can mean he/she/it shows

But Latin can still include the noun magistra when it wants to:

• identify who is doing the action
• make the sentence clearer
• add emphasis or contrast

So magistra is the explicit subject: the teacher.

Cur means why.

In this sentence it introduces an indirect question after ostendit:

• ostendit cur... = she shows/explains why...

This is different from a purpose clause. It is not in order that; it is literally an embedded why-question.

So the structure is:

• magistra plane ostendit
• cur discipuli nunc intro maneant

= the teacher clearly explains why the students should remain inside now

Because cur discipuli nunc intro maneant is an indirect question, and indirect questions in Latin normally take the subjunctive.

So:

• manent = they remain / they stay (indicative)
• maneant = they may remain / they should remain / they remain, in a subjunctive setting

Here the subjunctive is required by the grammar of the indirect question after cur.

It is present subjunctive because the staying is understood as simultaneous with or relevant at the same time as the main verb ostendit.

• ostendit = she explains / shows
• maneant = that they stay / should stay

So the teacher is explaining now why they are to remain inside now.

This fits normal sequence and sense in Latin: a present main verb can be followed by a present subjunctive in an indirect question when the action is contemporaneous.

Discipuli is nominative plural.

It is the subject of maneant:

• discipuli maneant = the students stay / should stay

Even though this is inside a subordinate clause introduced by cur, it still needs its own subject, and discipuli is that subject.

Here intro is an adverb meaning inside or indoors.

So:

• intro maneant = stay inside

A learner may expect intus, which also means inside. But intro can be used adverbially as well, especially with verbs of movement or position in some contexts. In this sentence it simply tells where the students are to remain.

So the phrase means remain indoors.

The semicolon shows that the sentence contains two closely related main clauses:

1. Haec via prorsus tuta non est nocte
2. magistra tamen plane ostendit cur discipuli nunc intro maneant

A period would separate them more strongly. A comma would be weaker and less suitable in formal English punctuation for two full clauses. The semicolon signals a strong connection between the ideas while still keeping them distinct.

No. It is an indirect question, not a purpose clause.

Why?

• It begins with cur = why
• It depends on a verb of explaining/showing: ostendit
• It asks for a reason, not a goal

A purpose clause would usually use ut or ne:

• ut discipuli intro maneant = so that the students may remain inside

But cur discipuli intro maneant means why the students should remain inside.

So this clause gives the content of what the teacher explains.