Nominalisation: Making Nouns from Verbs and Adjectives

A huge amount of Icelandic vocabulary is derived, not borrowed — and one of the most productive kinds of derivation is nominalisation: turning a verb or an adjective into a noun. Where English reaches for a Latinate suffix (examine → examination, beautiful → beauty), Icelandic builds the noun out of its own native material with a small set of suffixes, and — the part this page is really about — often changes the stem vowel as it does so. This page maps the regular routes: verb → action noun (in -ing/-un), present participle → agent noun (in -andi), and adjective → abstract quality noun (in -leiki/-d/-t/-ð). The single insight that makes the deadjectival nouns predictable instead of baffling: they trigger i-umlaut, the same vowel change you already know from comparatives. Learn that link and hæð, lengd, dýpt stop being random and start being derivable. (The general catalogue of affixes is on word-formation/derivation; the feminine declension of -ing/-un nouns is a noun-class topic on nouns/feminine-ing-un. Here the focus is the process: which suffix, and what happens to the vowel.)

Deverbal action nouns: -ing and -un

The two great action-noun suffixes are -ing and -un. Both attach to a verb and name the action or its result — the rough equivalent of English -ing / -tion / -ment. Both produce feminine nouns. The choice between them is largely lexicalised (you learn it per word), but a rough tendency holds: many verbs in -a of the kalla-type take -un (skoða → skoðun), while a great many others take -ing (byggja → bygging).

A few high-frequency action nouns are slightly irregular and worth learning as units rather than forcing into the pattern — most famously kenna "teach" → kennsla "teaching, instruction" (with an -sla suffix and an -nn-→-nn-s- adjustment), not *kenning in this sense (kenning exists but means "theory, doctrine"). These are the exceptions that prove the value of knowing the regular -ing/-un default.

Agent nouns from the present participle: -andi

Icelandic has a second, distinct route to a "doer" noun, separate from the -ari agents you met on word-formation/derivation. The present participle in -andi (originally "V-ing," as in hlæjandi "laughing") is nominalised into an agent noun — the person who does the action, as a role or category. Nema "to study/learn" → present participle nemandi → the noun nemandi "a student" (literally "one who is learning"). Stjórna "to direct/manage" → stjórnandi "a director, manager, conductor." These -andi agents are masculine and decline as such.

Why does Icelandic have two agent routes, -ari and -andi? Broadly, -ari gives a settled occupation/trade (kennari "teacher," bakari "baker"), while -andi gives "one who is (currently) V-ing," often a role, status, or participant (nemandi "student," stjórnandi "the one directing," eigandi "owner — one who owns," íbúi-type roles). The -andi form keeps a whiff of its participial "currently doing it" origin. For the learner the practical rule is to recognise both and reach for the established word — and to know that -andi nouns are real, frequent nouns (nemandi is among the first hundred words you learn), not merely participles.

Deadjectival abstracts — and the i-umlaut insight

Now the centrepiece. To turn an adjective into an abstract quality noun — "beautiful" → "beauty," "long" → "length" — Icelandic uses a few suffixes (-leiki, -leikur, -d, -t, -ð), and crucially, the short suffixes -d/-t/-ð systematically trigger i-umlaut on the stem vowel. This is the single most useful generalisation on the page, because it makes a whole class of "irregular-looking" nouns predictable.

Recall the i-umlaut outcomes you already know from irregular plurals and comparatives (pronunciation/i-umlaut-sound, adjectives/comparative-irregular): á/ó → æ, a → e, u → y, o → y/e. The deadjectival abstracts in -d/-t/-ð apply exactly these same changes:

Here is the elegant, memorable part — the link that ties this page back to grammar you already own. The vowel of the deadjectival abstract is the SAME as the vowel of the comparative. Compare:

This is not a coincidence — both the comparative and the deadjectival abstract are historically triggered by an i in the suffix, so both front the stem vowel the same way. The payoff for the learner is huge: if you know the comparative, you already know the abstract noun's vowel. Hærri → hæð, lengri → lengd, stærri → stærð. You don't have to memorise the vowel change twice; it's one change wearing two hats.

The longer suffix -leiki / -leikur also makes abstracts, especially from adjectives in -legur and many others, and — being longer and historically different — it usually does not umlaut: möguleg(ur) → möguleiki "possibility," fallegur → fallegleiki (or fegurð…), kærleikur "love" from kær. And one very common abstract is irregular and worth memorising on its own: fagur "beautiful" → fegurð "beauty" (with -urð and the a → e fronting). So the deadjectival system has two tracks: short -d/-t/-ð (umlauting), and longer -leiki/-leikur (usually not).

English vs Icelandic nominalisation

The conceptual machinery is familiar — every language nominalises — but two differences bite. First, English leans on Latinate suffixes (-tion, -ity, -ment, -ance) that have no place in Icelandic; the temptation is to anglicise ("konstrúksjón" instead of bygging, "signifikans" instead of þýðing), which is simply wrong. Icelandic builds from its own roots with -ing/-un/-leiki/-d, and a learner must reach for the native derivation, not a borrowed -tion. Second — and this is the part with no English parallel at all — the stem vowel changes. English "long → length" does shift the vowel (a historical i-umlaut survivor!), but it's a one-off oddity English speakers don't generalise. In Icelandic the vowel change is a live, systematic pattern tied to the comparative, so you must expect it: the abstract of djúpur is dýpt, not *djúpd. The learner who writes *djúpd, *langd, *háð has missed the umlaut — the single most common deadjectival error.

Common Mistakes

The headline transfer error: reaching for an English -tion noun instead of the native -ing/-un derivation. Icelandic purism is real; the borrowed form is not accepted.

The defining deadjectival mistake: forgetting the i-umlaut. The vowel must front — and it fronts to the same vowel as the comparative.

Not every agent is -ari; "student" is the -andi participle-noun nemandi. Recognise the two agent routes.

Some action nouns are lexicalised exceptions. Kenna gives kennsla "teaching" (the action) but kenning "theory" (a separate sense). Learn these as units.

Key Takeaways

• Verb → action noun: feminine -ing / -un (byggja → bygging, skoða → skoðun, þýða → þýðing). Don't borrow an English -tion word — Icelandic has the native form.
• Present participle → agent noun: masculine -andi (nema → nemandi "student," stjórna → stjórnandi "director"). A second agent route alongside -ari; -andi = "one who is V-ing."
• Adjective → abstract noun: short -d/-t/-ð (umlauting) and longer -leiki/-leikur (usually not): fagur → fegurð, mögulegur → möguleiki.
• The deadjectival abstracts in -d/-t/-ð trigger i-umlaut, the same change as the comparative: hár → hærri → hæð, langur → lengri → lengd, djúpur → dýpri → dýpt, þungur → þyngri → þyngd. Know the comparative and you know the abstract noun's vowel.
• The most common errors are anglicising (*konstrúksjón for bygging) and missing the umlaut (*langd for lengd). Build native; front the vowel.