Num quisquam scit cur porta hodie tam sero aperiatur?

Num introduces a yes/no question that usually suggests the speaker expects the answer no.

So:

• Num quisquam scit ... ? = Does anyone know ... ? / Surely no one knows ... ?

It gives the question a slightly skeptical tone. A learner should compare it with:

• -ne = neutral question
• nonne = question expecting yes
• num = question expecting no

Quisquam means anyone or anybody, especially in contexts like:

• negatives
• questions
• conditionals
• other non-assertive environments

Since num creates a yes/no question with a somewhat negative expectation, quisquam is very natural.

So:

• quisquam = anyone at all
• quis would not be the normal choice here

Because the sentence contains two different clauses:

1. Num quisquam scit ... ?
   This is the main clause, so scit is in the indicative.

2. cur porta hodie tam sero aperiatur
   This is an indirect question introduced by cur (why), and in Latin indirect questions normally take the subjunctive.

So:

• scit = indicative, main statement/question
• aperiatur = subjunctive, because it is inside an indirect question

This is one of the most important grammar points in the sentence.

It is an indirect question.

The direct version would be something like:

• Cur porta hodie tam sero aperitur?
  Why is the gate being opened so late today?

When that question becomes dependent on scit (knows), Latin changes the verb to the subjunctive:

• scit cur ... aperiatur
  knows why ... is being opened

So cur still means why, but the whole clause now functions as the object of scit.

Aperiatur is:

• present
• subjunctive
• passive
• third person singular

from the verb aperire = to open

So it means:

• may be opened
• or in this sentence more naturally, is being opened

Because it is passive, porta is the thing being opened.

Because porta is the subject of the passive verb aperiatur.

In English, we say:

• the gate is being opened

Here the gate is the grammatical subject, even though it is receiving the action.

So in Latin:

• porta = nominative singular, the gate
• aperiatur = is being opened

If the sentence were active, the gate would be the object instead.

Because sero here is an adverb, not an adjective.

• serus, sera, serum = late as an adjective
• sero = late as an adverb

In this sentence, it describes when the opening happens:

• tam sero = so late

It is not describing porta; it is modifying the verb aperiatur.

Tam means so, and sero means late.

Together:

• tam sero = so late

It can express surprise, complaint, or emphasis:

• Why is the gate being opened so late today?

Latin often uses tam to intensify an adjective or adverb.

It can mean either, depending on context, but gate is often the most natural meaning for porta, especially for a large entrance, city gate, or outer door.

So a learner should remember:

• porta = gate, door, or large entranceway

The exact English word depends on the situation.

Latin word order is much freer than English word order because Latin uses endings to show grammatical relationships.

English depends heavily on order:

• Does anyone know why the gate is being opened so late today?

Latin can arrange words more flexibly:

• Num quisquam scit cur porta hodie tam sero aperiatur?

A few points:

• num often comes near the beginning
• scit can appear early because it governs the indirect question
• cur introduces the subordinate clause
• hodie and tam sero are placed naturally for emphasis and flow
• aperiatur often comes at the end of its clause

So the Latin order is not random; it is just less rigid than English.

It belongs with the cur clause:

• cur porta hodie tam sero aperiatur
  why the gate is being opened so late today

It tells us when the opening is happening, so it modifies aperiatur, not scit.

In other words, the sentence is not mainly asking Does anyone know today...?
It is asking Does anyone know why the gate is opened so late today?

Not in standard classical grammar for this sentence.

• Cur porta hodie tam sero aperitur? = direct question
• Scit cur porta hodie tam sero aperiatur = indirect question

In an indirect question after scit, Latin normally uses the subjunctive. So aperiatur is the expected form.

Using aperitur here would go against the usual classical rule for indirect questions.

A helpful way to divide it is:

• Num = introduces the yes/no question, with an expected no
• quisquam = anyone
• scit = knows
• cur = why
• porta = the gate
• hodie = today
• tam sero = so late
• aperiatur = is being opened / may be opened

So the sentence is:

• a main yes/no question
• containing an indirect question

That makes it a very useful example of how Latin combines clause types.