Vowels in Icelandic can either be long or short. The long vowels take a slightly longer time to pronounce than the short vowels[a] and you often glide a bit into the long vowels. “Koma” (“to come”) is long, but “komma” (“a comma”) is short. “Vinur” (“friend”) is long but “vinnur” (“works”) is short.
The difference between a long and a short vowel is very small, and students usually find it difficult to distinguish between them. Students also tend to underestimate how long the long vowels are, and so they might pronounce “vinur” and “vinnur” the exact same way. It is much better to exaggerate the length of the long vowels. Exaggerating the difference makes it much easier to understand you. You can imagine “vinur” being written as “viiinur”.
The rules are:
  • A vowel is long if it has stress[1] and is followed by one consonant or no consonants.[b]
    • vinur, baka, læra, þá, tré, sofa, þak, útlönd (út-lönd), góð, afi
  • A vowel is short if it doesn’t have stress or if it’s followed by two or more consonants (like “mm”, “skt”, or “kk”).
    • vinnur, bakka, læi, boa, takk, gott, fiskur, amma, elstur

Gliding

There is another trick you can use to perfect your pronunciation. Long vowels are not static, instead they glide a bit into a fully open mouth. In English, when you pronounce the sad trombone sound “wah-wah”, you start with your mouth closed in the “w” and glide into the fully open-mouthed “ah”.
When you see a long vowel, try to both exaggerate its length and also exaggerate the amount of gliding you do, going from a closed mouth to an open mouth. Over-exaggerating it sounds better than not doing enough:
  • “mjög” is pronounced “mj(u)öööög”
  • “er” is pronounced “(i)eeeer”
  • “kom” is pronounced “k(u)oooom”