Learn Hardcore Icelandic: Hún æfir íslensku daglega með vini sínum. - She practices Icelandic daily with her friend.

Because íslenska is a weak feminine noun, and as the direct object of æfa, it takes the accusative singular, which is íslensku. For weak feminines in -a:

Nom: -a (íslenska)
Acc: -u (íslensku)
Dat: -u (íslensku)
Gen: -u (íslensku)

What case is vini in, and why?

Vini is dative singular of vinur (friend). The preposition með takes the dative when it means “together with/alongside,” so we get með vini. Declension (sg.):

Nom: vinur
Acc: vin
Dat: vini
Gen: vinar

Why is it sínum and not hennar?

Sínum is the 3rd-person reflexive possessive and refers back to the subject (Hún), meaning “her own.” Hennar is the non-reflexive “her,” which would refer to some other woman. So:

með vini sínum = with her own friend (the subject’s friend)
með vini hennar = with her friend (someone else’s friend)

Does sínum have to agree with vini?

Yes. Icelandic possessives agree with the noun they modify in case, number, and gender. Vini is dative masculine singular, so the possessive must be sínum (dative masculine singular).

Why does the possessive come after the noun (vini sínum)?

In Icelandic, possessives typically follow the noun: vinur minn, bókin þín, vini sínum. Preposing is possible for emphasis or style in some cases, but post-nominal is the default.

Can I place daglega somewhere else?

Yes. Common options include:

Hún æfir íslensku daglega með vini sínum.
Hún æfir daglega íslensku með vini sínum.
Hún æfir íslensku með vini sínum daglega. All are natural; word order can shift for rhythm or focus, but the meaning stays the same.

Is there another way to say “daily”?

Yes:

á hverjum degi (literally “on every day”)
dag hvern
daglega (adverb)
Example: Hún æfir íslensku á hverjum degi.

Could I use lærir or æfir sig instead of æfir?

Hún lærir íslensku = She is learning Icelandic (acquiring the language).
Hún æfir íslensku = She practices Icelandic (drills/uses what she knows).
Hún æfir sig í íslensku = She practices herself in Icelandic (very common with a preposition).
All are correct; choose based on nuance.

How do I say “She is practicing Icelandic right now”?

Use the progressive-like construction vera að + infinitive:

Hún er að æfa íslensku (núna).
Icelandic also often uses the simple present for current actions: Hún æfir íslensku (núna).

Are language names capitalized?

No. Unlike English, Icelandic does not capitalize language names. So íslenska is lowercase.

Can I drop the subject pronoun Hún?

No. Icelandic is not a pro-drop language in the modern standard. You normally keep the subject pronoun: Hún æfir…

How would I say “with her friends” (plural) or “with her female friend”?

Plural “friends”: með vinum sínum (dative plural of vinur
- reflexive).
Female friend: með vinkonu sinni (dative singular of vinkona
- reflexive).

What’s the difference between með + dative and með + accusative?

Með + dative = accompaniment/being together: Hún býr með hundi (She lives with a dog).
Með + accusative = bringing/using/having something: Hún kom með hund (She brought a dog), Hann skrifar með blýant (He writes with a pencil).
In our sentence, it’s companionship, so dative: með vini sínum.

How do I pronounce the tricky letters?

Hún: ú like long “oo” [uː].
æ in æfir: like the vowel in “eye” [ai].
ð in með: voiced “th” as in “this.”
í in íslensku/sínum: long “ee” [iː] when accented; short [ɪ] in unstressed short syllables (e.g., the second syllable of vini).
Stress is on the first syllable of each word.

Do I ever use the definite article with languages (e.g., íslenskuna)?

Generally no when speaking about a language in general: æfa íslensku, læra íslensku. You might see the definite form in specific contexts (e.g., contrasting “the Icelandic” of some text), but it’s uncommon in this meaning.

Is með sínum vini acceptable?

You may see með sínum vini, but the neutral, most common word order is með vini sínum. Preposed sinn can sound marked or emphatic; stick to post-nominal in normal speech.