sofa (to sleep) | Icelandic Grammar

sofa ("to sleep") is your first encounter with a genuinely strong verb that changes its stem vowel in every principal part. Where a weak verb like tala keeps its a throughout, sofa runs through three different vowels: o in the infinitive, e in the present (ég sef), and a/á in the past (ég svaf, við sváfum). There is no way to derive these from a rule — they must be learned as a set — but they follow the ancient ablaut pattern that runs through the whole strong-verb system, so the effort pays off across dozens of verbs.

Conjugation

Class: strong (ablaut series of the sofa / sefur / svaf / sváfu / sofinn type). Auxiliary: hafa — ég hef sofið "I have slept."

Principal parts
Infinitive	að sofa
3sg present	sefur
3sg past	svaf
3pl past	sváfu
Supine	sofið

Person	Present (nútíð)	Past (þátíð)
ég	sef	svaf
þú	sefur	svafst
hann / hún / það	sefur	svaf
við	sofum	sváfum
þið	sofið	sváfuð
þeir / þær / þau	sofa	sváfu

Person	Present subjunctive	Past subjunctive
ég	sofi	svæfi
þú	sofir	svæfir
hann / hún / það	sofi	svæfi
við	sofum	svæfum
þið	sofið	svæfuð
þeir / þær / þau	sofi	svæfu

Non-finite & imperative
Imperative (þú)	sofðu
Imperative (þið)	sofið!
Supine	sofið
Present participle	sofandi — "sleeping, asleep"

💡

The three vowels to fix in your memory are e–a–á: present sef / sefur, past singular svaf, past plural sváfum. Notice the past plural inserts a v and lengthens the vowel to á — this svaf → sváfum shift is the single thing learners get wrong most often.

The present: ég sef

This is the form that surprises everyone. The o of the infinitive becomes e in the present singular: ég sef, þú sefur, hún sefur. The plural reverts toward the infinitive vowel: við sofum, þið sofið, þau sofa. There is no u-umlaut to worry about here — sofum keeps its o (only short a umlauts), so do not write söfum.

Ég sef yfirleitt í átta tíma.

I usually sleep eight hours.

Barnið sefur loksins — vertu hljóður!

The baby's finally asleep — be quiet!

Sofðu vel, sjáumst á morgun.

Sleep well, see you tomorrow.

The past: svaf and sváfum

The past singular is svaf (note the new vowel a and the inserted v: s-v-a-f). The 2sg adds -st: þú svafst. The whole plural lengthens to á: við sváfum, þið sváfuð, þau sváfu.

Ég svaf hræðilega í nótt, það var svo heitt.

I slept terribly last night, it was so hot.

Við sváfum í tjaldi alla helgina.

We slept in a tent all weekend.

sofa vs sofna — "sleep" vs "fall asleep"

This is the distinction learners most need, and it is genuinely separate vocabulary. sofa is the state of sleeping; sofna (a weak verb: sofna / sofnaði / sofnað) is the transition into sleep — "to fall asleep." You cannot use sofa for the moment of dropping off.

Ég gat ekki sofnað fyrr en undir morgun.

I couldn't fall asleep until nearly morning.

Hann sofnaði fyrir framan sjónvarpið.

He fell asleep in front of the TV.

Think of it as a state-versus-change pair, like English "to sleep" versus "to fall asleep," or vera vakandi "to be awake" versus vakna "to wake up." Icelandic keeps the two cleanly apart with two different verbs, so reaching for sofa when you mean the onset of sleep is a meaning error, not just a stylistic one.

Useful idioms: sofa út and sofa hjá

sofa út means "to sleep in / have a lie-in" (literally "sleep out," i.e. sleep until you have had your fill). sofa hjá (+ dative) is the everyday way to say "to sleep with / have sex with" someone — useful to recognise so you do not say it by accident.

Um helgar reyni ég alltaf að sofa út.

At weekends I always try to sleep in.

Common Mistakes

❌ Ég sofa átta tíma á nóttu.

Incorrect — the present 1sg is sef, not the infinitive sofa; strong verbs change the stem vowel

✅ Ég sef átta tíma á nóttu.

I sleep eight hours a night.

❌ Ég sofaði illa í nótt.

Incorrect — sofa is strong; regularising the past to -aði is the classic error. The past is svaf

✅ Ég svaf illa í nótt.

I slept badly last night.

❌ Við svafum í tjaldi.

Incorrect — the past plural lengthens the vowel to á: sváfum, not svafum

✅ Við sváfum í tjaldi.

We slept in a tent.

❌ Ég svaf strax þegar ég lagðist.

Incorrect — for the moment of dropping off you need sofna ('fall asleep'), not sofa

✅ Ég sofnaði strax þegar ég lagðist.

I fell asleep as soon as I lay down.

Key Takeaways

sofa / sefur / svaf / sváfu / sofið — a strong verb with the ablaut vowels o → e → a → á.
Present singular sef / sefur (e-vowel), past singular svaf (a + inserted v), past plural sváfum (lengthened á).
No u-umlaut: sofum keeps its o (only short a umlauts).
sofna (weak) = fall asleep — a separate verb for the transition, not the state.
Idioms: sofa út (sleep in), sofa hjá (+ dat., sleep with someone).
Imperative sofðu; auxiliary hafa (ég hef sofið).

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