Olnboginn hennar er betri í dag, en henni er enn illt í úlnliðnum.

In Icelandic, a very common way to express possession is noun + definite article + possessive pronoun. So olnboginn hennar is a normal, natural way to say her elbow.

With body parts especially, this pattern is very common.
hennar olnbogi is possible, but it sounds more marked or contrastive, as if you are emphasizing that it is her elbow rather than someone else’s.

So for a neutral statement, olnboginn hennar is the expected choice.

They are different case forms of the pronoun meaning she/her:

• hennar = genitive, used for possession: her
• henni = dative, used in certain constructions such as henni er illt = she has pain / it hurts her

So:

• olnboginn hennar = her elbow
• henni er enn illt = she still has pain / it still hurts

This is a good example of how Icelandic pronouns change form depending on their grammatical role.

Betri is the comparative form of góður (good), so it means better when used as an adjective.

This adjective agrees with olnboginn, which is masculine singular. That is why the form is betri.

Compare:

• góður → betri → bestur
• olnboginn er betri = the elbow is better

Note that betur also means better, but betur is the adverb form, not the adjective form.

This is a very common learner question.

• betri is an adjective: it describes a noun
• betur is an adverb: it describes a verb, adjective, or whole situation

In this sentence, betri describes olnboginn, so it has to be the adjective form:

• Olnboginn er betri = The elbow is better

But with a verb, you would use betur:

• Henni líður betur = She feels better

So the choice depends on whether you are describing a thing or an action/state.

Because Icelandic often expresses pain with a special construction:

dative person + vera + illt + í + body part

So:

• henni er illt í úlnliðnum

literally looks something like to her is painful in the wrist, but idiomatically it means her wrist hurts or she has pain in her wrist.

This is a very common Icelandic pattern, similar to:

• Mér er illt í bakinu = My back hurts
• Honum er illt í fætinum = His leg hurts

So this is not strange Icelandic — it is the normal way to say this kind of thing.

In this construction, illt is used in the neuter singular as an impersonal predicate form.

It does not agree with henni or with úlnliðnum. Instead, Icelandic uses a fixed neuter-singular adjective in expressions like:

• mér er kalt = I am cold
• henni er heitt = she is hot
• honum er illt = he is in pain

So illt here is part of a standard impersonal pattern, not an adjective agreeing with the body part.

The preposition í takes:

• accusative for motion into something
• dative for location in something

Here the pain is located in the wrist, so Icelandic uses the dative:

• í úlnliðnum

The -num ending shows dative singular definite.

The definite article is also very natural here. Icelandic often uses the definite form with body parts in these expressions, especially when the owner is already clear from context:

• henni er illt í úlnliðnum = her wrist hurts

Because Icelandic often does not repeat the possessive with body parts when the owner is already obvious.

In henni er illt í úlnliðnum, the dative henni already tells you who is experiencing the pain. So Icelandic does not need to say her wrist explicitly again. It is understood as her wrist from the context.

English often repeats the possessor more than Icelandic does. Icelandic is happy to let the grammar make it clear.

They are two completely different words:

• en = but
• enn = still / yet

So in the sentence:

• ..., en henni er enn illt ...

the first one links two clauses: but
the second one is an adverb meaning still

This pair often confuses learners because the words look very similar, but their functions are different.

The dictionary form is úlnliður (wrist), a masculine noun.

Like many masculine nouns in -ur, it changes in the oblique cases, and the -ur disappears:

• nominative: úlnliður
• dative: úlnlið
• dative definite: úlnliðnum

So í úlnliðnum means in the wrist, with:

• úlnlið- = the stem
• -num = dative singular definite ending

This kind of noun change is very common in Icelandic declension.

Í dag is a fixed time expression meaning today.

Even though it is literally in day, Icelandic uses it as a set phrase, just like English uses today as a fixed word. You do not normally add the article here.

So:

• í dag = today
• í gær = yesterday
• á morgun = tomorrow

These time expressions are best learned as whole units.