Láttu mig vita ef þú kemur seint.

you

Breakdown of Láttu mig vita ef þú kemur seint.

• mig: me
• seint: late
• ef: if

Questions & Answers about Láttu mig vita ef þú kemur seint.

What does Láttu mean here, and what grammatical form is it?

Láttu is the 2nd person singular imperative (a command) of the verb láta (to let / to allow / to make / to have something done, depending on context).
In this sentence it works like English let in Let me know… → Láttu mig vita…

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Why is it mig and not ég for me/I?

Because Icelandic marks case. After láta in this pattern, the person being affected is in the accusative case.
So:

• ég = I (nominative, subject form)
• mig = me (accusative object form)

In Láttu mig vita, mig is the object of láttu.

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Why is vita in the infinitive (not conjugated)?

Because láta commonly takes another verb in the infinitive to express “let/make/have (someone) do something.”
So the structure is essentially:

Láttu + [object] + [infinitive]
→ Láttu mig vita = “Let me know” (literally “Let me know/let me ‘know’”).

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