Stelpan lærir á gítar.

Icelandic does not use a separate word before the noun for the.
Instead, it adds a definite ending to the noun.

• stelpa = girl
• stelpa
  • definite ending -n → stelpan = the girl

So Stelpan literally is “girl-the”, which functions exactly like English “the girl”.

They differ in definiteness:

• stelpa – a girl (indefinite)
  
  • Example: Þetta er stelpa. – This is a girl.
• stelpan – the girl (definite)
  
  • Example: Stelpan lærir á gítar. – The girl is learning (to play) guitar.

Same person, same gender, same case (nominative); only definiteness changes.

Stelpan is:

• the subject of the sentence
• in the nominative singular (subject) case
• feminine in gender

So grammatically: nominative, singular, definite, feminine noun used as subject.

lærir is the present tense, 3rd person singular of the verb að læra (to learn / to study).

Relevant forms:

• Infinitive: að læra – to learn
• 1st person singular: ég læri – I learn / am learning
• 2nd person singular: þú lærir – you learn / are learning
• 3rd person singular: hann / hún / það lærir – he / she / it learns / is learning

In Stelpan lærir á gítar, the subject is stelpan (she), so we use lærir.

Icelandic usually does not use a separate verb for “be” to make a present progressive (is learning, are learning).

• Stelpan lærir á gítar can mean:
  • The girl learns guitar. (habit)
  • The girl is learning guitar. (right now / in general)

So simple present in Icelandic often covers both English simple present and present continuous.

Icelandic can make a progressive-like form with “er að + infinitive”:

• Stelpan er að læra á gítar.
  Literally: The girl is at to learn on guitar.

This strongly suggests an ongoing action right now, similar to English is learning (right now).

With musical instruments, Icelandic normally uses the verb + á construction:

• að læra á gítar – to learn (to play) guitar
• að spila á gítar – to play guitar

You generally cannot drop á here.
*Stelpan lærir gítar sounds wrong / unidiomatic to native speakers.

So á is part of the idiom “læra á + instrument” = learn to play + instrument.

Literally, á often means on, but in this idiom it’s better to think:

• á gítar ≈ on guitar / the guitar as an instrument

So:

• lærir á gítar ≈ learns to play guitar
• spilar á gítar ≈ plays guitar

It is an idiomatic construction; translating á as plain on is too literal.

Here gítar is in the accusative singular after á in this idiom.

For this noun:

• Nominative singular: gítar
• Accusative singular: gítar

Since nominative and accusative look the same, you don’t see the case change in the form; you know it’s accusative because of the preposition + idiom (á gítar with an instrument).

You make gítar definite with a suffix, just like stelpan:

• gítar – (a) guitar
• gítarinn – the guitar

So:

• Stelpan lærir á gítar. – The girl is learning guitar (in general).
• Stelpan lærir á gítarinn. – The girl is learning the guitar (a specific guitar).

In practice, when talking about the skill, people normally use the indefinite: á gítar.

Yes, here it is the same basic Subject–Verb–Object/Prepositional phrase order:

• Subject: Stelpan – the girl
• Verb: lærir – learns / is learning
• Prepositional phrase: á gítar – on guitar

You would not say *Stelpan á gítar lærir in normal neutral speech. That sounds wrong; Icelandic prefers the same S–V–(rest) order in simple statements as English.

Approximate pronunciation (stressed syllables in caps):

• Stelpan – STEL-pan
  
  • e like e in get, a like a in father but short
• lærir – LAI-rir
  
  • æ like English eye; both r are tapped/trilled
• á – like ow in cow, but shorter and clearer
• gítar – GEE-tar
  
  • í like ee in see, stress on gí, clear t, rolled/trilled r

Whole sentence roughly: STEL-pan LAI-rir ow GEE-tar (with all main stress on the first syllable of Stelpan, then secondary stresses).

You need plural for both noun and verb:

• Stelpan lærir á gítar. – The girl learns / is learning guitar.
• Stelpurnar læra á gítar. – The girls learn / are learning guitar.

Changes:

• Stelpan (the girl, singular) → Stelpurnar (the girls, plural)
• lærir (3rd person singular) → læra (3rd person plural)

Yes, and it changes the meaning slightly:

• Stelpan lærir á gítar. – The girl is learning guitar (acquiring the skill).
• Stelpan spilar á gítar. – The girl plays guitar (she can already play / is playing).

Both use á gítar after the verb, but:

• læra á = learn to play
• spila á = play (an instrument)