Hún kann að spila á gítar.

Because hún is the subject form of she.

In this sentence, she is the person doing the action, so Icelandic uses the nominative form:

• hún = she
• hana = her
• henni = to her / for her

So Hún kann að spila á gítar means She knows how to play the guitar or She can play guitar, and hún is correct because she is the subject.

Here kann means knows how to or is able to because of learned skill.

That is important, because Icelandic often distinguishes between:

• kunna = to know how, to have learned a skill
• geta = can, be able to, be possible

So in this sentence, kann suggests that she has learned the skill of playing guitar.

For example:

• Hún kann að synda = She knows how to swim.
• Hún getur synt = She is able to swim / she can swim (in this situation).

In everyday English, both may translate as can, but Icelandic often keeps that distinction clearer.

In this sentence, að introduces the infinitive spila.

So the structure is:

• kann = knows how / can
• að spila = to play

Together:

• kann að spila = knows how to play

This is a very common pattern in Icelandic with kunna:

• kunna að lesa = know how to read
• kunna að elda = know how to cook

So the að here works a lot like English to in to play.

Yes, sometimes kunna can be used without að, especially before a direct object referring to something learned by heart or mastered.

For example:

• Ég kann þetta. = I know this.
• Hún kann lagið. = She knows the song.
• Þú kannt ensku. = You know English.

But when it means know how to do something followed by a verb, the pattern is commonly:

• kunna að + infinitive

So in your sentence, að is natural because it is followed by the verb spila.

Because Icelandic usually says spila á for playing a musical instrument.

So:

• spila á gítar = play guitar
• spila á píanó = play piano
• spila á fiðlu = play violin

The preposition á is part of the normal expression here. English does not need a preposition in play guitar, but Icelandic does.

So a learner should think of spila á as a set phrase when talking about instruments.

Both can be possible, but they mean slightly different things.

• á gítar = on guitar / guitar in a general sense
• á gítarinn would mean something more like on the guitar, referring to a specific guitar, and is usually not what you want in this kind of sentence

When talking about the ability to play an instrument in general, Icelandic normally uses the bare noun:

• spila á gítar
• spila á píanó

So á gítar is the natural form for play guitar as a skill.

Here gítar is in the accusative singular.

The preposition á can take different cases depending on meaning, but with spila á gítar the usual form is accusative.

For the noun gítar:

• nominative: gítar
• accusative: gítar

So in this particular word, nominative and accusative look the same, which means you do not see a visible change. But grammatically, it is treated as accusative in this expression.

Spila is very commonly used for:

• playing an instrument
• playing music
• playing games or sports in some contexts

Examples:

• spila á gítar = play guitar
• spila tónlist = play music
• spila skák = play chess
• spila fótbolta = play football

So spila is a broad verb, much like English play, but the patterns around it vary. For instruments, remember the expression spila á + instrument.

The basic order is:

• Hún = subject
• kann = finite verb
• að spila á gítar = infinitive phrase

So it follows a normal main-clause Icelandic word order: Subject + finite verb + rest

That gives:

• Hún kann að spila á gítar.

This is similar to English She can play guitar, except Icelandic uses að before the infinitive here.

In a yes/no question, the finite verb usually comes first:

• Kann hún að spila á gítar? = Can she play guitar? / Does she know how to play guitar?

So Icelandic switches from:

• Hún kann ... = She knows how... to:
• Kann hún ...? = Does she know how...?

This verb-first pattern is very common in Icelandic questions.

You add ekki after the finite verb:

• Hún kann ekki að spila á gítar. = She cannot play guitar / She does not know how to play guitar.

This is a very useful pattern:

• Ég kann ekki að synda.
• Við kunnum ekki að elda.

So the negative position here is: subject + finite verb + ekki + infinitive phrase

Yes. Kann is the present tense singular form of the verb kunna.

The infinitive is:

• kunna = to know, to know how

Some useful forms are:

• ég kann = I know how
• þú kannt = you know how
• hún/hann/það kann = she/he/it knows how
• við kunnum = we know how
• þið kunnið = you know how
• þær/þeir/þau kunna = they know how

So in your sentence, kann agrees with hún.

A careful approximation is:

Hún kann að spila á gítar ≈ hoon ka(n) ahth spi-la ow yee-tar

A few helpful notes:

• ú in hún is like oo
• ll is not in this sentence, so pronunciation is fairly straightforward
• að often sounds light and short in normal speech
• gítar has stress on the first syllable: GÍ-tar
• Icelandic words are usually stressed on the first syllable

A more natural connected pronunciation may sound smoother than the spelling suggests, especially with að.

Yes, absolutely.

Because kunna refers to learned ability or know-how, a very exact English translation is often:

• She knows how to play the guitar.

But natural English often prefers:

• She can play guitar.

Both are good translations, and the Icelandic sentence allows either. The difference is mostly in how natural the English sounds, not in a major change of meaning.