Frequency and Habitual Expressions | Icelandic Grammar

There are two ways to say how often something happens. One is the frequency adverbs — alltaf, oft, stundum, sjaldan, aldrei — which give a vague sense of frequency. The other is counting the occurrences exactly: once a day, twice a week, three times a year. Icelandic counting hides a small surprise English doesn't prepare you for: it has dedicated single-word adverbs for "once", "twice", and "three times" — einu sinni, tvisvar, þrisvar — and only switches to the regular number + sinnum pattern from four upward. This page covers the frequency scale, that one-to-three closed system, and how to attach a time period (á dag, í viku, á ári).

The frequency scale

For an approximate sense of "how often", Icelandic uses the same ladder of adverbs introduced on the time and frequency page. They answer hversu oft? ('how often?').

Icelandic	English
alltaf	always
oftast	most often / usually
oft	often
stundum	sometimes
sjaldan	rarely
aldrei	never

Ég fer oftast í ræktina eftir vinnu.

I usually go to the gym after work. — oftast 'most often / usually'.

Við borðum sjaldan úti.

We rarely eat out. — sjaldan 'rarely'.

Remember the placement rule: these adverbs come right after the finite verb (Ég fer oftast…), and aldrei ('never') is already negative, so it never takes an extra ekki.

einu sinni, tvisvar, þrisvar: the one-to-three set

Here is the feature competitors usually miss. For "one time", "two times", and "three times", Icelandic has special, single-word adverbs that you cannot build by simply gluing a number onto sinnum:

Icelandic	English	Note
einu sinni	once	literally "one time" (dative); set phrase
tvisvar (sinnum)	twice	dedicated adverb — NOT *tvö sinnum
þrisvar (sinnum)	three times	dedicated adverb — NOT *þrjú sinnum

The key warning: you do not say tvö sinnum for 'twice' or þrjú sinnum for 'three times'. The dedicated words tvisvar and þrisvar do that job. They can stand alone or be reinforced with sinnum (tvisvar sinnum), but the number words tvö, þrjú are not used here.

Ég hef komið hingað einu sinni áður.

I've been here once before. — einu sinni 'once'.

Hún hringir í mömmu sína tvisvar í viku.

She calls her mum twice a week. — tvisvar, the dedicated 'twice', not *tvö sinnum.

Við hittumst þrisvar í mánuði.

We meet three times a month. — þrisvar 'three times'.

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Think of einu sinni / tvisvar / þrisvar as a tiny closed club, like English "once / twice / thrice" — except that Icelandic actually uses "thrice" (þrisvar) in everyday speech, whereas English has retired it. From four up, both languages switch to the regular "N times" pattern.

From four up: number + sinnum

Once you reach four, the system becomes regular and predictable: take the cardinal number and add sinnum ('times'). Note that sinnum governs the dative, so the number that precedes it is in its dative form — fjórum (four), fimm (five), sex (six), and so on.

Icelandic	English
fjórum sinnum	four times
fimm sinnum	five times
tíu sinnum	ten times
hundrað sinnum	a hundred times

Ég hef séð þessa mynd fjórum sinnum.

I've seen this film four times. — number + sinnum from four up.

Hann fór tíu sinnum í sund í síðustu viku.

He went swimming ten times last week. — tíu sinnum 'ten times'.

Only the numbers that decline (one through four) change shape before sinnum; fimm and above are invariable, so fimm sinnum, sex sinnum, sjö sinnum are straightforward. For the cardinals above four, see cardinals 5 and up.

Attaching a time period: á dag, í viku, á ári

To say how often per period — "twice a week", "three times a day" — you add a prepositional phrase. The preposition depends on the period, and these are worth learning as fixed pairs:

Period phrase	English	Preposition
á dag	a / per day	á
í viku	a / per week	í
í mánuði	a / per month	í
á ári	a / per year	á

Ég bursta tennurnar tvisvar á dag.

I brush my teeth twice a day. — tvisvar + á dag.

Hún æfir fótbolta þrisvar í viku.

She practises football three times a week. — þrisvar + í viku.

Við förum til útlanda einu sinni á ári.

We go abroad once a year. — einu sinni + á ári.

Hann tekur lyfin sín fjórum sinnum á dag.

He takes his medicine four times a day. — fjórum sinnum + á dag.

The pattern is consistent: frequency expression + period phrase, in that order. Note that "day" and "year" take á (á dag, á ári) while "week" and "month" take í (í viku, í mánuði) — there is no deeper logic to extract here, so learn the four phrases as set pairs.

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The period nouns appear in fixed case after their prepositions: á dag and í viku (accusative), í mánuði and á ári (dative). You don't need to compute the case each time — just memorise the four phrases whole, the way you'd memorise "per day" in English.

Common Mistakes

❌ Ég fer í sund tvö sinnum í viku.

Incorrect — 'twice' is the dedicated adverb tvisvar, not the number tvö + sinnum.

✅ Ég fer í sund tvisvar í viku.

I go swimming twice a week.

❌ Hún hringir þrjú sinnum á dag.

Incorrect — 'three times' is þrisvar, not þrjú sinnum.

✅ Hún hringir þrisvar á dag.

She calls three times a day.

❌ Ég hef séð myndina fjögur sinnum.

Incorrect — sinnum takes the dative, so the number is fjórum, not the nominative/accusative fjögur.

✅ Ég hef séð myndina fjórum sinnum.

I've seen the film four times.

❌ Tvisvar á viku.

Incorrect preposition — 'week' takes í, not á: it's í viku.

✅ Tvisvar í viku.

Twice a week.

Key Takeaways

For approximate frequency, use the scale alltaf > oftast > oft > stundum > sjaldan > aldrei.
For exact counts, Icelandic has dedicated single-word adverbs for one to three: einu sinni, tvisvar, þrisvar — never tvö/þrjú sinnum.
From four up, the regular pattern is number (dative) + sinnum: fjórum sinnum, fimm sinnum, tíu sinnum.
Attach a period with a fixed preposition: á dag, í viku, í mánuði, á ári — learn these four as set phrases.
Order is frequency + period: tvisvar í viku, þrisvar á dag, einu sinni á ári.

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