Principal Parts

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by Siggi
Machine parts lying on a table.

Imagine that you’re learning English and you learn the verbs sing and fly. How do you know the past tense isn’t singed and flyed, like regular verbs? How do you know the past participle isn’t have singed and have flyed? How do you know that it’s sing, sang, have sung; fly, flew, have flown?

The answer is that you have memorised – probably subconsciously through extensive exposure to the language – the principal parts of these verbs. This has also sometimes been called key forms or verb paradigms.

Principal parts are the forms of a verb from which you can deduce all the other forms. For instance, if you know that it’s I flew (and not I flyed or I flow), then it’s obviously going to be you flew, he flew as well (and not you flyed or he flow). Principal parts are absolutely essential for conjugating Icelandic strong verbs in the past.

In English, the principal parts are the I past (I sang, I flew) and past participle (have sung, have flown). The Icelandic principal parts are actually quite similar.

What Are the Icelandic Principal Parts?

For weak verbs (-a verbs and -i verbs) there are 3 principal parts:

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

The infinitive is the base form of the verb, which you’ll find in the dictionary. The supine is the word form that follows the words geta and hafa.

Here’s gera (do) as an example. This image comes from BIN. In case you’re wondering about the word sagnorð in there, it means verb. BIN likes to show the word category.

  1. infinitive: gera
  2. ég past: ég gerði
  3. supine: ég hef gert

Weak verbs are usually regular enough that you don't actually need to bother with their principal parts. If you know that the verb you're dealing with is an -a verb or an -i verb, the infinitive is all the information you need to figure out all other forms, because they just don't change that much. að borða - ég borðaði - ég hef borðað, for instance, is quite straightforward.

To reliably and correctly conjugate strong verbs, though, it is essential to build a good mental library of principal parts. For that reason, we’ll be focusing on the principal parts of strong verbs from here on out.

For strong verbs there are 4 principal parts.

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

Here’s verða (become, will be, have to), one of the language’s most frequently-used verbs, as an example. Again, this is from BIN.

  1. infinitive: verða
  2. ég past: varð
  3. við past: urðum
  4. supine: orðið

How Do Principal Parts Work?

Principal parts are the forms of a verb from which you can deduce all the other forms. Specifically, you can use:

  1. the infinitive to predict the present tense, the present subjunctive, and the imperative
  2. the ég past to predict the past singular (þú, hann, hún, það, and hán)
  3. the við past can be used to predict the past plural (við, þið, þeir, þær, and þau), as well as the past subjunctive
  4. the supine can be used to predict the past participle

Let’s take a look at a couple of examples.

Að fá

The principal parts of are: 

Knowing just these 4 forms, let’s take a look at all the information we can deduce from that. 

Holy hell, that’s a lot of information! The power of principal parts!

The vowel shift in the present tense (á > æ) is regular and predictable. That’s why there isn’t a principal part for that.

Að gefa

The principal parts of gefa are:

Let’s see what we can deduce with that.

And lo: an absolute truckload of information just FALLS into our laps! Praise be to principal parts!

The vowel shift in the past subjunctive (á > æ) is regular and predictable. That’s why there isn’t a principal part for that.

Drawbacks of Principal Parts

Principal parts ARE great. They allow you to accurately predict nearly everything about nearly all verbs. However, principal parts aren’t perfect.

They don’t help with the present tense of meina (to mean), which has an -i verb past but an -a verb present. Þvo and sjá have a present tense vowel shift that their principal parts don’t predict. The ey-j-ur verbs and hybrid verbs have an unpredictable present tense, as well. Other irregularities exist which cannot be deduced from principal parts, such as the imperative of ganga and standa (gakktu and stattu, respectively).

Thankfully, some rebels don’t adhere perfectly to the “official” principal parts. For instance, Digicoll sometimes colours outside the lines to great effect.

Digicoll’s Take on Principal Parts

Nearly every student of Icelandic makes extensive use of Digicoll, and for good reason: it's the best free online Icelandic-English dictionary out there. And it has a... different take on principal parts than the rest of the language community. 

Instead of using the við past, Digicoll uses the þeir / þær / þau past. The two forms give the same exact information, so there’s no information lost, but there’s no upside either - there’s no reason to break with tradition here. If you ever find out why they do this, let me know, because this keeps me up at night.

Here’s lesa (read). The form (þeir) lásu would ordinarily be (við) lásum.

Remember the drawbacks of principal parts? They can’t predict words like þvo and sjá, or any of the hybrid verbs. Well, for many words, Digicoll goes ahead and adds a fifth principal part: the hann / hún / það / hán present. This fifth principal part totally takes care of those drawbacks! Why isn’t this standard in the principal parts model?

We can see that hanga has an unusual present tense that we wouldn’t have been able to predict with the regular 4 principal parts. Kudos, Digicoll!

Unfortunately, Digicoll is pretty inconsistent about using this fifth principal part. Here’s heita (to be called), which has a weak present tense, unpredictable from the traditional four principal parts. There’s no extra help from Digicoll this time. Boo, Digicoll.


Principal parts are (supposedly) the forms of a verb with which you can deduce all the other forms. For strong verbs, those are the:

  1. infinitive
  2. ég past
  3. við past
  4. supine

For weak verbs, the við past is unnecessary, as it’s easily predictable.

Quite a few verbs, unfortunately, have an unpredictable present tense. You can check out my article on hybrid verbs and ey-j-ur verbs for details on those.

Digicoll has its own take on principal parts, adding information about the present tense. I honestly don’t understand why that isn’t the standard for principal parts everywhere. 

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