Очевидно, поезд опаздывает.

Because очевидно is being used as an introductory word here, meaning something like obviously, evidently, or apparently from the speaker’s point of view.

So the structure is:

Очевидно, поезд опаздывает.
= Obviously, the train is late / is running late.

In Russian, introductory words are often separated by commas.

Compare:

• Очевидно, поезд опаздывает. = Obviously, the train is late.
• Это очевидно. = This is obvious.

In the second sentence, очевидно is not introductory; it is part of the main statement, so there is no comma.

Here, очевидно functions as an introductory word rather than a regular adverb.

That means it does not describe the verb опаздывает directly in the same way an ordinary adverb would. Instead, it comments on the whole sentence: the speaker is saying that the fact is obvious.

A useful way to think about it:

• Очевидно, поезд опаздывает.
  = It is obvious / obviously, the train is late.

So grammatically, it is best understood as a parenthetical or introductory element.

Because поезд is the subject of the sentence.

The verb опаздывает means is late or is running late, and the thing doing that is the train. Subjects in Russian are normally in the nominative case.

So:

• поезд = train (nominative singular)
• поезд опаздывает = the train is late

Опаздывает is the imperfective present tense form of опаздывать, which means to be late / to run late / to arrive late habitually or as an ongoing situation.

In this sentence, the idea is that the train is currently late, so Russian naturally uses:

• поезд опаздывает = the train is late / is running late

By contrast, опоздает is the perfective future form of опоздать, meaning will be late.

Compare:

• Поезд опаздывает. = The train is late / is running late.
• Поезд опоздает. = The train will be late.

So опаздывает is correct for a present situation.

Because in Russian, just like in English, the present tense can describe a current state or ongoing situation.

So:

• поезд опаздывает literally means something like the train is being late / is arriving late
• in natural English, we usually say the train is late or the train is running late

Russian often expresses this idea with a verb where English may prefer an adjective:

• Russian: Поезд опаздывает.
• English: The train is late.

So the structure is normal and idiomatic in Russian.

Опаздывать means to be late, to run late, or to arrive later than expected.

It can be used with people, vehicles, events, and so on:

• Я опаздываю. = I’m late.
• Автобус опаздывает. = The bus is late.
• Он всегда опаздывает. = He is always late.

So in your sentence, поезд опаздывает means the train is not on time.

Yes. Russian word order is more flexible than English word order, though the neutral version here is:

Очевидно, поезд опаздывает.

You could also say:

• Поезд, очевидно, опаздывает.
• Поезд опаздывает, очевидно.

These versions are possible, but they may sound slightly different in emphasis or style.

The original version is very natural if you want to begin with the speaker’s comment: Obviously...

They are very close in meaning, but punctuation matters.

Очевидно, поезд опаздывает clearly treats очевидно as an introductory word:
Obviously, the train is late.

If you write Поезд очевидно опаздывает, many speakers would still understand it, but Russian normally prefers commas with introductory очевидно:

• Поезд, очевидно, опаздывает.

That is the safer standard written form.

So for learners, it is best to remember:

• sentence-initial: Очевидно, ...
• in the middle: ..., очевидно, ...

The stress is:

• очеви́дно
• по́езд
• опа́здывает

So the whole sentence is:

Очеви́дно, по́езд опа́здывает.

A rough English-style approximation would be:

a-chee-VEED-na, PO-yezd a-PAZ-di-va-yet

A few notes:

• поезд has two syllables: по-езд
• здыв in опаздывает can feel difficult at first, so it helps to say it slowly: о-па́з-ды-ва-ет

Sometimes yes, but the nuance can change.

Очевидно most often means:

• obviously
• evidently
• sometimes apparently, depending on context

In this sentence, obviously or evidently is usually the best match, because the speaker presents the conclusion as clear.

So:

• Очевидно, поезд опаздывает.
  = Obviously, the train is late. = Evidently, the train is late.

Apparently can work in some contexts, but in English it sometimes suggests less certainty than obviously.

No extra word is required here.

Russian does not use a present-tense equivalent of is in the same way English does. Also, the main predicate here is the verb опаздывает, so the sentence is already complete.

Structure:

• Очевидно = introductory comment
• поезд = subject
• опаздывает = verb

So the sentence is fully grammatical as it stands.

It is similar, but not exactly the same.

• Поезд опаздывает = The train is late / running late
• Поезд задерживается = The train is delayed

The second version focuses more on the delay itself, while опаздывает focuses on the fact that it is not on time.

In many real situations, both could fit, but they are not perfect synonyms. Your original sentence is the straightforward way to say The train is late.