munu is the closest thing Icelandic has to a pure future tense marker — an auxiliary meaning roughly "will," used to make a prediction about what is going to happen. It is defective: it has no infinitive use as a normal verb, no supine, and no participle, existing only as a present-tense paradigm plus a past-subjunctive paradigm. That past form, myndi, has taken on a life of its own as the standard "would" auxiliary of Icelandic conditionals. Getting munu right is largely a matter of distinguishing the three "future-ish" auxiliaries — munu (prediction), skulu (commitment/obligation), and ætla (intention) — which English collapses into a single "will / going to."
Conjugation
Type: preterite-present (the same archaic class as kunna, muna, eiga, mega, skulu), defective. It is followed directly by a bare infinitive (no að): það mun rigna "it will rain." Its forms below are everything it has — there is no supine, no past participle, and no present-participle in normal use.
| Principal parts | |
|---|---|
| Infinitive | að munu |
| 1sg present | mun |
| 1sg past (subjunctive) | mundi / myndi |
| Supine | — (none) |
| Past participle | — (none) |
| Person | Present (nútíð) | Past / conditional (þátíð vmh.) |
|---|---|---|
| ég | mun | myndi (mundi) |
| þú | munt | myndir (mundir) |
| hann / hún / það | mun | myndi (mundi) |
| við | munum | myndum (mundum) |
| þið | munuð | munduð |
| þeir / þær / þau | munu | myndu (mundu) |
A few notes on this table. In the present, watch the singular: ég mun, þú munt, hann mun — the 1st and 3rd person are bare mun (no ending), and the 2nd person adds -t, the classic preterite-present pattern, not -ur. The plural is regular: munum, munuð, munu.
The past set is functionally a past subjunctive ("would") and has two spellings in free variation: the older mundi/mundir/mundum/mundu and the now-dominant myndi/myndir/myndum/myndu. The y-spelled forms are far more common in modern writing and speech for the conditional sense; you will see mundi in older or more formal texts. (The 2pl munduð keeps u in both.) Because munu is defective, there is no past indicative distinct from this — the "past" of munu simply is the conditional myndi.
munu = prediction: "it will (turn out to) happen"
The core meaning of present munu is a prediction or expectation about the future — the speaker forecasts that something will be the case, without claiming to control it. This is why munu is the natural choice for weather, outcomes, and statements about how things will go. It is somewhat more formal and declarative than the everyday ætla að; you meet it constantly in forecasts, news, and considered statements.
Það mun rigna í allan dag samkvæmt spánni.
It's going to rain all day according to the forecast. — pure prediction: það mun rigna. The weather doesn't 'intend' anything; munu forecasts it.
Þetta mun allt reddast á endanum.
It'll all work out in the end. — mun expresses confident prediction about how things will turn out. A very common, reassuring use.
Ég mun aldrei gleyma þessum degi.
I will never forget this day. — a solemn, declarative 'will': munu, not ætla, gives this its weight.
myndi = "would": the conditional auxiliary
The past form myndi is, for most learners, the more useful half of the verb: it is the standard way to build a conditional "would + verb." It pairs with the past subjunctive in the if-clause to express hypotheticals.
Ef ég ætti meiri pening myndi ég ferðast meira.
If I had more money I'd travel more. — myndi + infinitive = 'would travel'. The if-clause uses the past subjunctive ætti.
Hvað myndir þú gera í mínum sporum?
What would you do in my shoes? — myndir (2sg) þú gera = 'would you do'. The everyday way to ask a hypothetical.
munu vs skulu vs ætla: the crucial contrast
English uses "will / going to" for all of these, which is exactly why learners reach for the wrong Icelandic auxiliary. The three are genuinely distinct:
| Auxiliary | Core meaning | Typical use |
|---|---|---|
| munu | prediction / expectation | forecasts, declarations, "it will (turn out)" |
| skulu | commitment / obligation / firm resolve | promises, instructions, "shall / is to" |
| ætla (að) | intention / plan | everyday "going to," personal plans |
So Ég mun koma "I will come" is a prediction ("it will be the case that I come"); Ég skal koma "I'll come (you have my word)" is a commitment; and Ég ætla að koma "I'm going to come" is a stated intention/plan. For ordinary "I'm going to do X" in conversation, ætla að is by far the most natural; munu sounds more like a forecast or a written register; skulu adds the flavour of a promise or a directive.
Ég skal hjálpa þér með þetta, engar áhyggjur.
I'll help you with this, don't worry. — skal = a personal commitment/promise, NOT a neutral prediction. Using mun here would sound oddly detached.
Ég ætla að fara í ræktina eftir vinnu.
I'm going to go to the gym after work. — ætla að = a plan/intention. This is the everyday 'going to'; mun would sound like a forecast about yourself.
Common Mistakes
❌ Ég mun fara í ræktina eftir vinnu.
Odd — for a personal plan, use intention 'ætla að fara'. mun makes it sound like a detached prediction about yourself, not a decision.
✅ Ég ætla að fara í ræktina eftir vinnu.
I'm going to go to the gym after work.
The most common misuse is reaching for munu where intention (ætla að) is meant. munu forecasts; ætla plans.
❌ Ég mun hjálpa þér, ég lofa.
Mismatched — a promise wants commitment 'skal', not the neutral prediction 'mun'. (You can use mun in writing, but with 'ég lofa' the natural auxiliary is skal.)
✅ Ég skal hjálpa þér, ég lofa.
I'll help you, I promise.
For promises and firm undertakings, skulu carries the commitment that munu lacks.
❌ Ég hef munað að klára þetta.
Incorrect — munu has NO supine; you cannot form a perfect with it. It is defective: present 'mun' and conditional 'myndi' only.
✅ Ég mun klára þetta.
I will finish this. (and for the conditional: 'ég myndi klára þetta' — I would finish this.)
Treating munu as a full verb with a supine/participle is a structural error. It simply doesn't have those forms.
❌ Það mun að rigna á morgun.
Incorrect — munu takes a BARE infinitive, no 'að'. It's 'mun rigna', not 'mun að rigna'.
✅ Það mun rigna á morgun.
It will rain tomorrow.
Like the modals, munu is followed directly by the infinitive with no linking að.
Key Takeaways
- munu is the defective future auxiliary: present mun / munt / mun / munum / munuð / munu, conditional myndi (mundi) / myndir / myndi / myndum / munduð / myndu. No supine, no participle.
- Present munu makes a prediction ("it will, it'll turn out"): það mun rigna.
- Past myndi is the everyday "would" of conditionals: ég myndi fara.
- It takes a bare infinitive (no að).
- Keep the three apart: munu = prediction, skulu = commitment/obligation, ætla að = intention/plan. For ordinary spoken plans, prefer ætla að.
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- Expressing the Future: munu, ætla, presentB1 — How Icelandic expresses future time despite having no inflected future tense — the bare present plus a time adverb as the default, munu + infinitive for predictions, ætla að + infinitive for intention, and verða að for obligation-tinged futures, with the munu / ætla / skulu split that carves up English 'will'.
- The Conditional with myndi ('would')B1 — The periphrastic conditional myndi + infinitive ('would do') — the Icelandic auxiliary that lines up most neatly with English 'would' (ég myndi fara 'I would go'). myndi is the past subjunctive of munu, used in the result clause of counterfactuals and in polite hypotheticals, but idiomatic Icelandic often prefers a BARE past subjunctive instead (ég færi over ég myndi fara), and statives strongly prefer væri/ætti/gæti — 'would be' is væri, never *myndi vera.
- munu vs skulu vs ætla: Future and IntentionB2 — English 'will / shall / going to' splits across three Icelandic verbs. munu makes a neutral PREDICTION ('it will rain', formal future); skulu expresses the speaker's COMMITMENT — a promise in the 1st person, a command in the 2nd ('I'll definitely help', 'you shall go'); ætla að states an INTENTION or plan ('I'm going to study tonight'). The key is that skal is performative — saying it commits you — a force English 'shall' has mostly lost, so ég skal is stronger than 'I will', and munu is a forecast, never a plan. Includes a decision table.
- skuluB1 — Full paradigm of the defective preterite-present skulu 'shall' — present skal/skalt/skal/skulum/skuluð/skulu and past subjunctive skyldi…, with no supine and no participle. skal is a performative: in the first person it makes a promise ('I shall, you have my word'), in the second a command ('you are to'). The past skyldi is the 'should/was to' of reported obligation, and við skulum is the standard 'let's'. Distinguishing skulu (commitment) from munu (prediction) and ætla (intention) is the key to using it correctly.
- ætla (to intend / be going to)A2 — Full conjugation of the weak Class-1 verb ætla (ætla / ætlaði / ætluðu / ætlað), the everyday near-future construction ætla að + infinitive, the reflexive ætla sér, and how it differs from vilja and munu.