Hún tekur þátt í þessum hópi einu sinni í viku.

She takes part in this group once a week.

Breakdown of Hún tekur þátt í þessum hópi einu sinni í viku.

• hún: she
• þessi: this
• í: for
• vikan: the week
• hópur: the group
• taka þátt í: to take part in
• einu sinni: once

Questions & Answers about Hún tekur þátt í þessum hópi einu sinni í viku.

What does "tekur þátt í" literally mean, and is it always used for "participates"?

Literally, "tekur þátt í" means "takes a part in".

• taka = to take
• þáttur = part, share → þátt here is the accusative singular
• í = in
  So taka þátt í einhverju = to take part in something → to participate in something.

This is the standard, idiomatic way to say to participate (in) in Icelandic.
Examples:

• Ég tek þátt í verkefninu. – I take part in / participate in the project.
• Viltu taka þátt í leiknum? – Do you want to take part in the game?

So yes: when you want to say “participate in” something, taka þátt í is usually what you use.

Why is it "tekur" and not "taka"?

"taka" is the infinitive form: to take.
In a sentence with a subject, you need a conjugated form.

Here, the subject is hún (she), 3rd person singular, present tense.
The present tense of taka is:

• ég tek – I take
• þú tekur – you take (singular)
• hann / hún / það tekur – he / she / it takes
• við tökum – we take
• þið takið – you (plural) take
• þeir / þær / þau taka – they take

So with hún, you correctly get hún tekur.

What grammatical pattern does "taka þátt í" have? Which cases does it use?

The pattern is:

taka þátt í + [dative object]

• taka þátt – the verb plus its direct object (þátt = part, accusative)
• í + dative – the preposition í takes the dative for “in” (location or membership)

In this sentence:

• þátt – accusative object of taka
• í þessum hópi – “in this group”, with hópi in the dative after í

So overall pattern:
[Subject] + tekur þátt í + [something in the dative].

Why is it "í þessum hópi" and not "í þessi hópur" or something similar?

Because í in the sense of “in (inside / as a member of)” takes the dative case, and both words have to match that:

• Base words:
  
  • þessi hópur – this group (nominative)
• Dative singular forms:
  
  • þessum – this (masc./fem. dative singular)
  • hópi – group (masculine dative singular)

So:

• í þessum hópi = in this group (correct dative)
• í þessi hópur is ungrammatical because þessi hópur is nominative, not dative.

What gender and declension does "hópur" have, and how do we get "hópi"?

"hópur" means group and is:

• masculine
• a regular -ur masculine noun

Singular declension:

• Nominative: hópur – a group / the group (subject form)
• Accusative: hóp – I see a group
• Dative: hópi – in / with / from a group
• Genitive: hóps – of a group

In our sentence, after í we need the dative, so we use hópi.

Why is there both "þessum" and "hópi"—does Icelandic have a separate word for “this” AND a definite ending on the noun?

Yes, Icelandic can show “definiteness” in two ways, but you normally don’t use both at once:

1. Definite ending on the noun
   
   • hópurinn – the group
2. Demonstrative + noun (this/that)
   
   • þessi hópur – this group
   • sá hópur – that group

In our sentence, we use a demonstrative:

• í þessum hópi – in this group

Because þessum already makes it specific (“this”), you don’t also add a definite ending like -num (you would not say í þessum hópnum in this meaning).

What does "einu sinni í viku" literally mean, and why does it mean “once a week”?

Literally:

• einu – one (neuter, dative singular of einn)
• sinni – time, occasion (dative singular of sinn)
• í viku – in a week / per week (accusative of vika, week)

So word-for-word:
einu sinni í viku ≈ one time in (a) week → idiomatically once a week.

It describes a repeated, regular action: she participates every week, one time per week. It does not mean just one single time during a week.

Why are "einu" and "sinni" in those forms—why not just "ein sinn"?

"einu sinni" is a fixed expression meaning once.

Grammatically:

• einu is dative neuter singular of einn (one).
• sinni is dative singular of sinn (time, occasion in this idiom).

The phrase einu sinni is almost always used in this exact form; you simply learn it as the set phrase for “once”.

Other related expressions:

• tvisvar – twice
• þrisvar sinnum – three times
• margsinnis – many times

But for “once”, it’s specifically einu sinni.

Why is it "í viku" and not "í vika"? Which case is "viku"?

"vika" (week) is feminine. Its singular forms:

• Nominative: vika – a week
• Accusative: viku – (for) a week
• Dative: viku – (in) a week
• Genitive: viku – of a week

So viku is the accusative here, but accusative and dative look the same in singular.

In expressions of duration or rate, Icelandic typically uses the accusative:

• einu sinni í viku – once per week
• tvisvar í mánuð – twice a month
• þrjá tíma í dag – three hours today

So í viku in this context is understood as per week and uses the accusative.

Does this sentence mean she is doing it right now, or regularly? How does tense work here?

"Hún tekur þátt í þessum hópi einu sinni í viku." describes a habitual / regular action:

• She regularly takes part in this group, with the frequency once a week.

Icelandic present tense is used for:

• Actions happening now
• Habitual or repeated actions (like English present simple: She goes..., She works...)

The phrase einu sinni í viku makes it clear that this is not just right now, but her regular pattern.

Can I change the word order, e.g. put the time expression earlier in the sentence?

You have some flexibility, as long as the finite verb stays in 2nd position (V2 rule in main clauses).

Neutral order (as in your sentence):

• Hún tekur þátt í þessum hópi einu sinni í viku.

You can also front the time expression:

• Einu sinni í viku tekur hún þátt í þessum hópi.
  Once a week, she takes part in this group.

Both are grammatically fine and natural. What you can’t do is move the finite verb away from the second position, e.g.:

• ✗ Hún þátt tekur í þessum hópi… – incorrect
• ✗ Einu sinni í viku hún tekur þátt… – incorrect (verb must be 2nd: tekur needs to come right after Einu sinni í viku or after Hún, depending on what you put first).

How do you pronounce the tricky parts, especially "þátt" and "hópi"?

Key points:

• þ in þátt
  
  • Pronounced like unvoiced English “th” in thin, thing.
• á in þátt
  
  • A long “ow” sound, like English “how”, but a bit shorter and tenser.

• Final -tt in þátt

  • A short, hard t sound (often with a bit of pre-aspiration in Icelandic, but as a learner you can just aim for a clear t).
• ó in hópi
  
  • Like a long “o” in “go”, but tenser and purer (no diphthong).
• Stress:
  
  • In Icelandic, stress is almost always on the first syllable:
    
    • HÚN tekur ÞÁTT í ÞESSum HÓpi EINu SINni í VÍku.

You don’t have to sound perfect; being roughly close on þ and the vowel lengths already helps a lot with clarity.