You have already met the workhorse rule of Swedish spelling on Double Consonants and Vowel Length: a stressed vowel is long before a single consonant, short before a double consonant (kal [kɑːl] "bare" vs kall [kal] "cold"). The letters m and n are the great exception to how that rule is written — and they are the two consonants English speakers misspell most often. The good news is that the exception is not chaos: it is positional, completely predictable, and once you see the shape of it, kom but komma stops looking like a contradiction and starts looking like the rule doing exactly what it should.
The core rule: single at the end, double before a vowel
Here is the whole thing in one sentence. m and n are written single at the end of a word (and before another consonant), but double between vowels when the stressed vowel is short. The doubling only appears when there is a following vowel to "carry" the second letter — typically when an ending is added.
That means the same short vowel can sit in front of a single m/n in one form and a double m/n in another, with no change in pronunciation:
Jag glömde nyckeln hemma igen.
I left the key at home again. — glömde has single m before a consonant; hemma has double m between vowels.
Kom in, det är kallt ute!
Come in, it's cold out! — kom (the imperative/past form) ends single; the infinitive komma doubles before -a.
Han är en lugn man.
He's a calm man. — man ends single; but mannen ('the man') doubles the n before the ending.
For every other consonant, a short stressed vowel triggers doubling everywhere, including at the end: kall, vass, tjock, full. Only m and n suppress the final double — so you write hem, not *hemm; man, not *mann; kom, not *komm.
Why it works this way
The logic is that a final m or n has nothing after it, so there is no risk of misreading the vowel as long — Swedish simply does not bother to double a nasal at the very end of a word. The moment a vowel-initial ending attaches (the plural -ar, the definite -en, the infinitive -a, the verb endings), the consonant is now wedged between two vowels, and the short vowel must be protected from being read long. So the second m or n reappears.
Compare the two situations side by side:
| Base form (single m/n) | Inflected form (double m/n) | Why |
|---|---|---|
| kam (comb) | kammen (the comb), kammar (combs) | ending adds a vowel → double m |
| man (man) | mannen (the man), männen (the men) | ending adds a vowel → double n |
| kom (came / come!) | komma (to come), kommer (comes) | infinitive/present add a vowel → double m |
| vän (friend) | vännen (the friend), vänner (friends) | ending adds a vowel → double n |
| dum (stupid) | dumma (stupid, plural/definite) | ending adds a vowel → double m |
Jag kammar håret varje morgon.
I comb my hair every morning. — kam ends single, but the verb kammar doubles the m before -ar.
Vad dum jag är! Vi gjorde precis samma dumma misstag igen.
How stupid I am! We just made the same stupid mistake again. — predicative dum is single; the attributive dumma doubles the m.
The adjective trap: dum → dumt → dumma
Adjectives are where English speakers get burned, because the three agreement forms hide the rule in plain sight. Take dum "stupid":
- dum (en-word, basic) — single m, because it is word-final.
- dumt (ett-word / neuter) — still single m, because the m is now before a consonant (the -t), not before a vowel.
- dumma (plural and definite) — double m, because the ending -a is a vowel.
So the doubling switches on and off purely according to what follows the m. The neuter -t form keeps the single m (it is a consonant cluster), and only the vowel-initial -a form doubles it.
Det var dumt av mig.
That was silly of me. — dumt keeps single m: the -t is a consonant, so no doubling.
Sluta ställa så dumma frågor.
Stop asking such silly questions. — dumma doubles the m before the vowel ending -a.
Lampan är trasig och rummet är tomt.
The lamp is broken and the room is empty. — lampa and rummet both show medial double m; tomt keeps single m before the consonant -t.
The same pattern runs through tom (empty) → tomt / tomma, trim, grym (cruel) → grymt / grymma, and the verbs: glömma (to forget) → glömde / glömt / imperative glöm. Notice that the past glömde and supine glömt drop back to a single m, because the m is again before a consonant.
Glöm inte att låsa dörren — jag glömde det igår.
Don't forget to lock the door — I forgot to yesterday. — glöm (imperative) and glömde (past) both single, glömma (infinitive) doubles.
When m genuinely IS doubled at the end
There is a small, real set of words that keep mm at the end — and they exist precisely to disambiguate from a single-m word with a long vowel. These are not exceptions to memorise blindly; each one is a minimal pair where the double m signals the short vowel that the single m could not.
| Double mm (short vowel) | Single m (long vowel) |
|---|---|
| damm (dust; pond) [dam] | dam (lady) [dɑːm] |
| lamm (lamb) [lam] | lam (lame, paralysed) [lɑːm] |
| ramm (ram, battering beak) [ram] | ram (frame) [rɑːm] |
Det är så mycket damm under sängen.
There's so much dust under the bed. — damm with mm, short a, distinct from dam 'lady'.
Vi åt lamm med rosmarin.
We had lamb with rosemary. — lamm with mm; lam (one m) would mean 'lame'.
This handful aside, the default at the end of a word is single m. Final nn does not occur this way at all in modern native spelling — n at the end of a word is essentially always single (man, vän, in, mun, kvinn- → kvinna only doubles medially). So the "keep the double" cases are limited to that short mm list; for n, trust the single-final rule completely.
After å, ä, ö it works identically
The rule does not care which vowel precedes the nasal — it applies after the extra letters å, ä, ö exactly as after a, o, u. Keep the å/ä/ö intact (they are separate letters, never optional), and apply the same single-at-the-edge, double-in-the-middle logic:
Jag måste sy om sömmen i byxorna.
I have to redo the seam in the trousers. — söm 'seam' is single at the end; sömmen ('the seam') doubles the m before -en.
Glöm det — vi glömmer det aldrig.
Forget it — we'll never forget it. — glöm (single, final) vs glömmer (double, medial).
Hon är den klokaste kvinnan jag känner.
She's the wisest woman I know. — kvinna / kvinnan with medial double n; the noun never appears with a final nn.
Common Mistakes
❌ Jag vill komm hem.
Incorrect — komma doubles the m only because it's medial (before -a). The bare imperative/short form is kom, single m. But the infinitive here needs the full komma.
✅ Jag vill komma hem.
I want to come home. — infinitive komma, medial mm.
❌ Han är en snäll mann.
Incorrect — n is single at the end of a word: man. The double n only appears medially, as in mannen ('the man').
✅ Han är en snäll man.
He's a kind man.
❌ Det var ett dumt beslut, vi är så duma.
Incorrect — failing to restore the double m when the vowel ending is added. The plural is dumma, not *duma.
✅ ... vi är så dumma.
... we are so stupid. — dumma doubles the m before -a.
❌ Stäng dörren och kamm ditt hår.
Incorrect — two errors: kam is single at the end (a comb), and the verb 'comb' is kamma/kammar — but here you want the verb kamma, not the noun. Single-final kam ≠ the verb form.
✅ Stäng dörren och kamma ditt hår.
Close the door and comb your hair. — verb kamma, medial mm.
❌ Det ligger så mycket dam under sängen.
Incorrect — dam (single m, long vowel) means 'lady'. 'Dust' is damm with mm to mark the short vowel.
✅ ... så mycket damm under sängen.
... so much dust under the bed.
Key Takeaways
- The general rule (double consonant = short vowel) holds, but m and n are written single at the word edge and double only between vowels.
- So hem, kam, man, kom, dum, vän end single; hemma, kammar, mannen, komma, dumma, vänner double the nasal medially. The vowel stays short throughout — only the spelling moves.
- In adjectives, the neuter -t form keeps the single nasal (dumt, tomt) because -t is a consonant; the vowel-initial -a form doubles it (dumma, tomma).
- A few words keep final mm to disambiguate: damm (dust) vs dam (lady), lamm (lamb) vs lam (lame), ramm vs ram (frame).
- Final nn essentially never occurs in native words — trust single-final n completely.
- komma (mm, medial) vs kom (m, final) is the rule in miniature: same verb, spelling flips with the consonant's position.
Now practice Swedish
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Start learning Swedish→Related Topics
- Double ConsonantsA2 — A doubled consonant marks a short, stressed vowel before it (vit vs vitt, glas vs glass). The doubling simplifies before another consonant (känna → känt) and the letters m and n break the rule at the end of a word — a stubborn exception that trips up even advanced learners.
- Swedish Spelling: OverviewA2 — Swedish spelling is fairly regular and largely phonemic — but you must master double consonants for vowel length, the soft/hard g and k, the many spellings of the sje-sound, and the iron rule that compounds are written as ONE word, since splitting them (särskrivning) is the most stigmatised error in the language.
- Present Tense: Group 1 (-ar)A1 — The single most useful conjugation rule in Swedish: for the giant, fully regular Group 1 class, the present tense is just the infinitive plus -r (tala → talar, arbeta → arbetar, fråga → frågar). No stem change, no person endings. Because every new and borrowed verb joins Group 1, mastering this one rule unlocks the bulk of the Swedish verb lexicon.