In a language where almost every adjective bends to its noun in gender, number and case, the present participle in -andi is a startling exception: used adjectivally, it does not inflect at all. Spennandi bók "an exciting book," spennandi bækur "exciting books," spennandi myndum "to/with exciting films" — the adjective is spennandi every single time. After years of training to flex every modifier, learners reflexively try to make it agree (*spennandar bækur), and that is the central error this page exists to kill. We will see why -andi is frozen, how it behaves attributively and predicatively, how many of these forms have hardened into ordinary dictionary adjectives, and how to keep it apart from two things it is not: the declining -aður past participle (treated on Past Participles as Adjectives) and the vera að progressive (on verbs/progressive-vera-ad). The -andi form's other lives — as an agent noun, and its derivation — are on word-formation/present-participle-andi; here we stay strictly on its adjectival use.
The form: how -andi is built
The present participle is formed by adding -andi to the verb stem: spenna "to excite/tense" → spennandi "exciting," krefja(st) "to demand" → krefjandi "demanding," renna "to run/flow" → rennandi "running," éta "to eat" → ætandi "edible/eatable," koma "to come" → komandi "coming/next." The class is fully productive: in principle any verb can throw off an -andi form, so this is an open, ever-growing set of adjectives. They correspond closely to English -ing adjectives (exciting, demanding, running), which is a helpful anchor — but with the crucial difference that the Icelandic form never changes shape.
Þetta er ótrúlega spennandi bók.
This is an incredibly exciting book. — spennandi (from spenna) with feminine 'bók'; the form is bare.
Ég drekk bara rennandi vatn, ekki úr pollum.
I only drink running water, not from puddles. — rennandi (from renna 'to flow') with neuter 'vatn'; still bare.
Þetta er mjög krefjandi verkefni.
This is a very demanding project. — krefjandi (from krefjast 'to demand') with neuter 'verkefni'.
Attributive -andi is indeclinable — the showcase
The defining behaviour is best seen by forcing the same -andi word across genders, numbers and cases on different nouns. Watch spennandi refuse to move:
| Noun phrase | Gender / number / case | Adjective form |
|---|---|---|
| spennandi bók | fem. sg. nom./acc. | spennandi |
| spennandi bækur | fem. pl. nom./acc. | spennandi |
| spennandi mynd | fem. sg. | spennandi |
| spennandi verkefni | neut. sg. | spennandi |
| spennandi tími | masc. sg. | spennandi |
| á spennandi tímum | masc. pl. dat. | spennandi |
| til spennandi staða | masc. pl. gen. | spennandi |
A normal adjective would give góð bók / góðar bækur / gott verkefni / góðum tímum — seven different shapes in those slots. Spennandi gives one. That is the whole phenomenon. (It belongs, accordingly, to the catalogue of indeclinable adjectives on adjectives/indeclinable.)
Við sáum spennandi mynd og fengum spennandi fréttir sama kvöldið.
We saw an exciting film and got exciting news the same evening. — feminine singular 'mynd' and feminine plural 'fréttir' both take the identical 'spennandi'; no -ar plural, no agreement.
Þetta hefur verið mjög spennandi tími fyrir okkur.
This has been a very exciting time for us. — masculine 'tími', and still 'spennandi'; the gender change makes no difference.
Hún vinnur við krefjandi störf á krefjandi tímum.
She works in demanding jobs in demanding times. — neuter plural 'störf' and masculine dative plural 'tímum', both with the unchanging 'krefjandi'.
Why it doesn't inflect
This is not an arbitrary exception; it follows from the shape of the word. Icelandic adjectives inflect by attaching an ending to a stem — but -andi already ends in an unstressed -i, and that -i is part of the suffix, not an inflectional slot waiting to be filled. The inflection has nothing to grab: there is no consonant-final stem to add -ur/-t/-ar to, and the final -i cannot itself be swapped because it is lexical, not grammatical. This is exactly the same mechanism that freezes the -a/-i adjectives like sammála and hugsi (see adjectives/indeclinable): a final unstressed vowel that the paradigm cannot treat as "stem + ending." So -andi is indeclinable for a principled morphological reason, and recognising that shape is what stops you from hypercorrecting it.
Predicate use: after vera it is still bare (with a wrinkle)
Used predicatively — after vera "to be" or another linking verb — the adjectival -andi is also typically invariant: bókin er spennandi "the book is exciting," verkefnin eru krefjandi "the projects are demanding," fréttirnar voru spennandi "the news was exciting." Here the contrast with ordinary adjectives is sharp: a normal adjective agrees with the subject in the predicate (bækurnar eru góðar, fem. pl.), but the -andi adjective stays put (bækurnar eru spennandi).
Bókin er æðislega spennandi en svolítið löng.
The book is wonderfully exciting but a bit long. — predicate 'spennandi' invariant after feminine 'bókin'; contrast 'löng' (long), an ordinary adjective agreeing as feminine.
Verkefnin eru krefjandi en mjög gefandi.
The projects are demanding but very rewarding. — two -andi adjectives ('krefjandi', 'gefandi') with neuter plural 'verkefnin', both bare; a normal adjective would show -in/-ir/-ar agreement.
Þetta var spennandi, en líka þreytandi.
This was exciting, but also tiring. — neuter subject 'þetta'; 'spennandi' and 'þreytandi' both invariant. (Note: þreytandi 'tiring' is the -andi adjective; þreyttur 'tired' is the declining -aður type — see below.)
The wrinkle worth flagging at C1: a handful of -andi forms have been partly drawn back toward inflection in the spoken language, and you may rarely meet a "neuter" -andi in very careful or older writing — but the safe, standard, and overwhelmingly common practice is to leave all adjectival -andi forms uninflected, attributively and predicatively. Treat it as invariant and you will be right essentially always.
Lexicalised -andi adjectives: dictionary words now
Many -andi forms have drifted away from their verbs and become ordinary dictionary adjectives — you reach for them without thinking of the verb at all. Spennandi "exciting" is felt as a plain adjective, not "tensing"; likewise heillandi "charming, captivating," aðlaðandi "attractive, appealing," afgerandi "decisive," viðeigandi "appropriate, fitting," ráðandi "dominant, ruling." These are participial in origin but adjectival in every use — and they too stay indeclinable. Lexicalisation does not unlock inflection; a lexicalised -andi is still frozen.
Hann er afar heillandi maður og mjög aðlaðandi.
He is an extremely charming man and very appealing. — 'heillandi' and 'aðlaðandi', lexicalised -andi adjectives, both bare with masculine 'maður' / predicate; lexicalisation doesn't make them inflect.
Þetta var ekki viðeigandi athugasemd.
That was not an appropriate remark. — 'viðeigandi' (appropriate), a fully lexicalised -andi adjective, invariant before feminine 'athugasemd'.
The contrast that defines the type: -andi vs the declining -aður
The cleanest way to fix the -andi rule is to set it beside the other verbal adjective, the past participle in -aður/-inn, which does decline fully (see Past Participles as Adjectives). The same root can yield both, and they behave oppositely:
| Present participle (-andi) | Past participle (-aður/-inn) | |
|---|---|---|
| Form | spennandi, krefjandi | spenntur/spennt/spennt, lokaður/lokuð/lokað |
| Meaning | active: 'exciting', 'demanding' | passive/resultative: 'excited/tense', 'closed' |
| Inflection | indeclinable — one form | fully declining — agrees in gender/number/case |
| Example | spennandi bækur (always) | lokaðar dyr / lokuð hurð / lokað hlið |
So spennandi "exciting" never moves, but spenntur "tense/excited" (from the same verb spenna) inflects like any adjective: hann er spenntur, hún er spennt, þau eru spennt, spenntir áhorfendur "excited spectators." The pair spennandi (active, frozen) vs spenntur (resultative, agreeing) is the single best mnemonic for the whole topic: -andi is alive but rigid; -aður/-inn is alive and flexible.
Spennandi leikur — og spenntir áhorfendur.
An exciting match — and excited spectators. — SAME verb spenna: 'spennandi' (the match is exciting) is indeclinable; 'spenntir' (the spectators are excited), the -tur past participle, agrees as masculine plural. The two participles, opposite behaviour.
Myndin var spennandi og allir voru spenntir.
The film was exciting and everyone was excited. — predicate 'spennandi' (invariant) for the film vs. 'spenntir' (masc. pl. agreeing) for the people. The active -andi freezes; the resultative -tur flexes.
Common Mistakes
❌ Þetta eru spennandar bækur.
Incorrect — the -andi adjective is indeclinable; it takes NO feminine-plural -ar (or any) ending. The form stays 'spennandi'.
✅ Þetta eru spennandi bækur.
These are exciting books. — one invariant form for every gender, number and case.
The flagship error: applying the relentless agreement habit to a frozen word. Spennandi has no plural, no feminine, no case forms.
❌ Verkefnið er spennandit.
Incorrect — no neuter -t is added to an -andi adjective, even before/after a neuter noun. It stays 'spennandi'.
✅ Verkefnið er spennandi.
The project is exciting. — predicate -andi is invariant, no neuter -t.
The neuter -t is the most tempting ending (it appears on nearly every other adjective in the neuter); -andi still refuses it.
❌ Áhorfendurnir voru mjög spennandi. (meaning 'the spectators were excited')
Wrong participle — 'spennandi' means 'exciting' (active); 'excited' (resultative) is the declining 'spenntir' (masc. pl.). 'The spectators were exciting' is not what you mean.
✅ Áhorfendurnir voru mjög spenntir.
The spectators were very excited. — use the -tur past participle 'spenntir', which agrees, for the resultative 'excited'.
Choosing -andi (active "exciting") where you mean the resultative "excited" reverses the meaning — a real and common confusion, because English "excited/exciting" maps onto exactly this -andi / -aður split.
❌ Hún var heillandi mig allt kvöldið. (meaning 'she was charming me')
Wrong construction — this reads -andi as a progressive ('was charming [verb]'), which Icelandic does NOT do. For the ongoing action use vera að: 'hún var að heilla mig'. As an adjective heillandi means 'charming (in nature)'.
✅ Hún var heillandi. / Hún var að heilla mig allt kvöldið.
She was charming. / She was charming me all evening. — adjective 'heillandi' (charming) vs. the progressive 'vera að + infinitive' for the action.
Icelandic has no -andi progressive ("be + -ing"); the progressive is vera að + infinitive (verbs/progressive-vera-ad). Reading adjectival -andi as a running action is an English-transfer error.
Key Takeaways
- The present participle in -andi used adjectivally is indeclinable: one form for every gender, number and case (spennandi bók, spennandi bækur, spennandi verkefni, spennandi tímum).
- This holds attributively and predicatively (bókin er spennandi); a normal adjective would agree, but -andi does not — a rare island of non-inflection.
- The reason is morphological: -andi ends in an unstressed -i that is part of the suffix, leaving the inflection no stem-plus-slot — the same mechanism as sammála, hugsi.
- The class is productive and many forms are lexicalised dictionary adjectives (heillandi, aðlaðandi, viðeigandi, afgerandi); lexicalisation does not unlock inflection — they stay frozen.
- Keep it apart from two things it is not: the declining -aður/-inn past participle (spenntur/spennt/spennt, lokaðar dyr), which agrees and gives the resultative "excited/closed"; and the progressive, which is vera að
- infinitive, never -andi.
- The mnemonic pair: spennandi (active "exciting", frozen) vs spenntur (resultative "excited", agreeing) — same verb, opposite behaviour.
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- The Present Participle in -andiB2 — The Icelandic present participle in -andi (talandi 'speaking', hlaupandi 'running'): used adverbially (hann kom hlaupandi 'he came running'), attributively (rennandi vatn 'running water'), and as the base for a productive class of agent nouns (nemandi 'student', eigandi 'owner', stjórnandi 'manager'). The crucial trap: -andi is NOT an English-style progressive — 'I am reading' is never *ég er lesandi but ég les / ég er að lesa. The form is largely indeclinable when adverbial/predicative, while the agent nouns decline as masculines (nemandi → pl. nemendur).
- Indeclinable AdjectivesB2 — The small but high-frequency set of Icelandic adjectives that do not inflect at all — sammála 'in agreement', hugsi 'pensive', gjaldþrota 'bankrupt', the whole -a/-i-final type, the -andi participials (spennandi), and invariant loan colours (kakí, bordó) — which keep one form across every gender and case and so must NOT be 'corrected' into agreeing.
- The Progressive: vera að + InfinitiveA2 — Icelandic's optional progressive — vera að + infinitive (ég er að lesa 'I am [in the middle of] reading') — used to stress that an action is in progress right this moment, contrasted with the plain present, and the idiomatic preterite var að meaning 'just (now) did'.