Nenio okazas en tiu sceno.

Nenio means nothing.

It is made from:

• neni- = the no-/none- series
• -o = a noun ending

So nenio is literally no thing / nothing.

Related words in the same series include:

• neniu = no one / nobody / none
• neniam = never
• nenie = nowhere
• neniel = in no way

In Esperanto, when you already use a neni- word like nenio, you normally do not add ne.

So:

• Nenio okazas. = Nothing happens.

But:

• Nenio ne okazas. is generally considered wrong or at least nonstandard, because it creates an unnecessary double negative.

A good rule:

• If you use nenio, neniu, neniam, nenie, etc., that already makes the sentence negative.

Okazas means happens or is happening.

It comes from the verb okazi = to happen / to occur.

Breakdown:

• okaz- = the verb root
• -as = present tense

So:

• okazas = happens / is happening / does happen

In this sentence, Nenio okazas means Nothing is happening or Nothing happens.

In Esperanto, all present-tense verbs end in -as.

Some basic verb endings are:

• -as = present
• -is = past
• -os = future
• -us = conditional
• -u = command / wish
• -i = infinitive

So:

• okazi = to happen
• okazas = happens / is happening
• okazis = happened
• okazos = will happen

Because okazi and esti mean different things.

• okazi = to happen / occur
• esti = to be

So:

• Nenio okazas = Nothing happens
• Nenio estas = Nothing is

The second sentence would usually not express the same idea. If you want to say that no action or event is taking place, okazas is the natural choice.

En tiu sceno means in that scene.

Word by word:

• en = in
• tiu = that
• sceno = scene

So the whole phrase tells you where nothing is happening: in that scene.

Depending on context, sceno could refer to:

• a scene in a film
• a scene in a play
• a scene in a story
• sometimes a visual scene

Because tiu and tio are used differently.

• tiu = that one / that before a noun
• tio = that thing

Since sceno is a noun, Esperanto uses tiu:

• tiu sceno = that scene

You would not normally say:

• tio sceno

That is incorrect.

Because here sceno is not a direct object. It is part of a prepositional phrase:

• en tiu sceno = in that scene

Normally, a noun after a preposition like en does not take -n when it shows location.

So:

• en la sceno = in the scene
• en tiu sceno = in that scene

You might see en with -n when it shows movement into something:

• Mi iras en la ĉambron. = I go into the room.

But here there is no movement, only location, so sceno stays without -n.

Yes, you could absolutely say:

• En tiu sceno nenio okazas.

That means the same thing, but it puts more emphasis on in that scene.

Esperanto word order is fairly flexible because grammar is shown clearly by endings and function words. Still, the most neutral order here is:

• Nenio okazas en tiu sceno.

So both are correct:

• Nenio okazas en tiu sceno.
• En tiu sceno nenio okazas.

The difference is mainly emphasis and style.

It can mean either, depending on context.

Esperanto present tense -as often covers both:

• nothing happens
• nothing is happening

So:

• Nenio okazas. could be a general statement
• or it could describe what is happening right now

The surrounding context tells you which English translation is best.

Usually yes, and it is a close cognate, so it is easy to remember.

Sceno can mean:

• a scene in a play
• a scene in a movie
• a scene in a book or story
• sometimes a visual scene

In this sentence, the most likely meaning is a scene in some narrative or visual work.

Yes, but it means something slightly different.

• en tiu sceno = in that scene
  Focus: the event takes place within that scene as a unit of story or film.

• dum tiu sceno = during that scene
  Focus: the time span while that scene is happening.

Often these will be very similar in practice, but en tiu sceno is usually the more natural choice when talking about what occurs within a particular scene of a film, play, or story.

The structure is:

• Nenio = subject
• okazas = verb
• en tiu sceno = prepositional phrase showing location/context

So literally:

• Nothing happens in that scene.

This is a very normal Esperanto sentence pattern:

• subject + verb + prepositional phrase

It is simple and idiomatic.