Lestin seinkar í dag, svo við bíðum rólega.

Lest means train, while lestin means the train.

In Icelandic, the definite article is usually attached to the end of the noun instead of being a separate word like English the. So:

• lest = train
• lestin = the train

Here, lestin refers to a specific train that both speaker and listener know about.

Seinkar is the present tense, 3rd person singular form of að seinka.

In this sentence, the subject is lestin, which is singular, so the verb is also singular:

• ég seinki = I delay / I am delayed
• þú seinkar
• hann/hún/það seinkar
• við seinkum
• þið seinkið
• þeir/þær/þau seinka

Here, Lestin seinkar means something like The train is delayed or The train is running late.

Because Icelandic often uses a full verb where English uses to be plus an adjective or participle.

English says:

• The train is delayed

But Icelandic can simply say:

• Lestin seinkar

So seinkar already carries the idea of is delayed / is running late. You do not need er here.

Í dag means today.

It is a fixed time expression in Icelandic:

• í dag = today
• á morgun = tomorrow
• í gær = yesterday

Even though í often means in, you should learn í dag as a whole expression meaning today.

Here, svo means so or therefore.

It connects the two clauses:

• Lestin seinkar í dag = The train is delayed today
• svo við bíðum rólega = so we wait calmly

So svo is showing result or consequence.

Depending on context, svo can also mean other things, such as then or like that, but here so / therefore is the right meaning.

Við means we, and bíðum is the present tense, 1st person plural form of að bíða, meaning to wait.

So:

• við bíðum = we wait / we are waiting

The ending -um is a very common ending for we forms in Icelandic verbs.

Not exactly.

In English, you usually say wait for someone/something. In Icelandic, bíða often takes its object directly, traditionally in the genitive, without a separate word meaning for.

For example:

• Við bíðum lestarinnar = We are waiting for the train

In your sentence, there is no object after bíðum, so it just means we wait or we are waiting in general.

Because rólega is an adverb, not an adjective.

It describes how the waiting happens:

• rólega = calmly

It does not describe we, so it does not agree with við in gender or number.

A useful pattern is that many Icelandic adverbs are formed with -lega, similar to English -ly:

• fallegur = beautiful

• fallega = beautifully

• rólegur = calm
• rólega = calmly

Yes. You could also say:

• Í dag seinkar lestin, svo við bíðum rólega.

That is also correct.

A useful thing to notice is Icelandic main-clause word order: the finite verb usually stays in the second position. So if you move í dag to the front, the verb comes next:

• Í dag seinkar lestin
• not Í dag lestin seinkar

This is a very important Icelandic pattern.

The comma separates two full clauses:

• Lestin seinkar í dag
• við bíðum rólega

Since svo links them, the comma helps show the break between the two thoughts. In normal written Icelandic, this is very natural.