Conjugating Strong Verbs in the Past Tense

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by Siggi
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“Strong verb” is what we call verbs that change their stem when we conjugate them. English is full of strong verbs: to sing - I sang; to fly - I flew; to drive - I drove. So is Icelandic.

I’m not gonna sugarcoat it: conjugating strong verbs in the past tense is probably the single most challenging part of verb conjugation. They are notoriously irregular, with semi-predictable vowel shifts as well as some completely unpredictable consonant changes in some verbs. The only way to really learn the irregularities is by memorising principal parts, which are 4 forms of a strong verb you have to just memorise to deduce everything else.

The endings, thankfully, are quite regular, and that’s what we’ll be focusing on here. 

If you’re wondering how you can tell which verbs are strong verbs, check out my Overview of the Icelandic Verb System.

If you’d like to check out how to conjugate strong verbs in the present tense, I’ve got you covered right here.

Now, let's make conjugating strong verbs in the past tense a little easier! 

Rule of Thumb

Basically, it works like this:

  1. remove the infinitive ending (if there is one)
  2. change the stem vowel
  3. add the appropriate ending

Notice that the plural endings (við, þið, þeir, þær, þau) are identical to those of -a verbs and -i verbs. Icelandic is merciful like that.

How Can I Tell How the Vowel Changes?

How can you tell? Well, there’s the rub.

Usually, you can’t tell how the vowel will change, at least not from just looking at the infinitive. You have to rely on principal parts

I go in depth about principal parts here, but basically they are the 4 forms of a strong verb you have to just memorise to deduce everything else. Those 4 are:

  1. the infinitive
  2. the ég past (past tense 1st person singular)
  3. the við past (past tense 1st person plural)
  4. the supine

To make the past tense, we use the:

  • ég past to form the singular forms (ég, þú, hann, hún, það, hán), and the
  • við past to form the plural forms (við, þið, þeir, þær, þau)

I’ll give you the principal parts for the verbs we use here so you don’t need to look them up.

Adding the Ending

Let’s take verða, koma, and fara as examples. These are 3 of the most frequently used strong verbs. Their principal parts are:

Remember: we’ll use the ég past as the stem for the singular, and the við past as the stem for the plural. Let’s take a look at each in turn.

Here’s the singular, formed from the ég past (ég varð, ég kom, ég fór).

And here’s the plural, formed from the við past (við urðum, við komum, við fórum).

Just as an overview, here are those tables all together.

Pronouncing the Unpronounceable

Let’s take a special look at halda (hold, think), lesa (read), and detta (fall, trip). For reference, here are their principal parts.

Adding the -st ending for þú results in a consonant cluster that’s unpronounceable in Icelandic. 

  • hélt + st = héltst
  • las + st = lasst
  • datt + st = dattst

It would be very weird if every conversation ran into a screeching halt when you run into something unpronounceable like that, so instead we just make them a little easier to pronounce and keep on talking.


Strong verbs are hideously irregular in the past tense, and there’s no remedy for that but some good-old brute force rote memorisation. Principal parts play a big role in that. 

As for the step-by-step instructions, it’s as “easy” as 1-2-3:

  1. remove the infinitive ending
  2. change the stem vowel
  3. add the appropriate ending

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