Það er mögulegt að ég komi seint í kvöld.

Það er is a very common Icelandic way to make an impersonal statement, like English it is in it is possible.

Here það does not refer to a specific thing. It works like a dummy subject, just as English it does in sentences like:

• It is possible
• It is important
• It is strange

So Það er mögulegt... means It is possible...

Mögulegt is the neuter singular form of the adjective mögulegur meaning possible.

It appears in the neuter here because it is used in an impersonal structure with það er. In this kind of sentence, Icelandic normally uses the neuter singular adjective:

• Það er gott — It is good
• Það er skrýtið — It is strange
• Það er mögulegt — It is possible

So the -t ending is exactly what you expect here.

Here að means that and introduces a subordinate clause.

So the sentence breaks down like this:

• Það er mögulegt — It is possible
• að ég komi seint í kvöld — that I may come late tonight

This use of að is extremely common after expressions like:

• Það er líklegt að... — It is likely that...
• Það er gott að... — It is good that...
• Ég held að... — I think that...

Because this sentence uses the subjunctive, not the ordinary indicative form.

The verb koma means to come. Its present indicative first person singular is kem:

• Ég kem seint í kvöld — I am coming / will come late tonight

But after an expression of possibility such as Það er mögulegt að..., Icelandic often uses the subjunctive:

• að ég komi

So komi is the present subjunctive form of koma.

This signals uncertainty, possibility, or non-factual meaning. In other words, the speaker is not stating the arrival as a fact, only as something that may happen.

Yes, komi is grammatically a present-tense form, specifically present subjunctive.

But Icelandic often uses present forms when talking about the future if the time is clear from context. Here the phrase í kvöld already tells us the event is in the future, so Icelandic does not need a separate future tense form.

That is why this can be understood as:

• that I come late tonight
• more natural English: that I may come late tonight
• or that I might arrive late tonight

So the tense is present in form, but the meaning is future because of the time expression.

Seint means late. It is an adverb here, describing how or when the coming happens.

Compare:

• seinn — late as an adjective, for a masculine noun
• sein — feminine
• seint — neuter or adverbial use

In this sentence it is adverbial, so seint is the correct form:

• ég komi seint — I come / arrive late

Í kvöld means tonight or more literally this evening.

This phrase is used for the evening of the current day:

• í kvöld — tonight / this evening

By contrast:

• í nótt means tonight in the sense of during the night
• á kvöldin means in the evenings or on evenings in a habitual sense

So í kvöld is the natural choice if you mean that the speaker may come late this evening / tonight.

The order is quite normal for Icelandic.

Inside the subordinate clause introduced by að, the usual order is:

• subject: ég
• verb: komi
• adverb: seint
• time phrase: í kvöld

So:

• að ég komi seint í kvöld

A very literal structure would be that I come late tonight.

This is simpler than main-clause word order in Icelandic, where verb-second rules are very important. In a subordinate clause like this one, the order is often more straightforward.

Yes, but it means something different.

• Ég kem seint í kvöld = I am coming / will come late tonight
  • This sounds more direct and factual.
• Það er mögulegt að ég komi seint í kvöld = It is possible that I may come late tonight
  • This expresses uncertainty.

So both are correct, but they are not interchangeable. The first states a plan or expectation more directly; the second presents it as only a possibility.

Yes, it is correct and natural. Það er mögulegt að... is a standard way to say it is possible that...

That said, Icelandic also often uses modal expressions that may sound a little more conversational, for example:

• Ég gæti komið seint í kvöld — I might come late tonight
• Það gæti verið að ég komi seint í kvöld — It could be that I come late tonight

So your sentence is perfectly good, but in everyday speech many speakers might prefer one of those alternatives depending on context.