Learn Hardcore Turkish: O, dinlerken not alıyor, bu yüzden daha iyi hatırlıyor. - While she is listening, she takes notes, so she remembers better.

O is the third person singular pronoun. It can mean he, she, or it depending on context.
Turkish does not mark gender in pronouns, so you understand whether it is he or she from the wider context or from earlier sentences. In this sentence alone, it could be any of the three.

Why is there a comma after O (O, dinlerken not alıyor)? Is that required?

The comma after O is stylistic; it is not grammatically required.
You can write the sentence as:

O dinlerken not alıyor, bu yüzden daha iyi hatırlıyor.

Both versions are correct. The comma can be used in writing to give a small pause after the subject, but in everyday texts it is often omitted.

What exactly does dinlerken mean, and how is it formed?

dinlerken means while (he/she/they) is listening or when (he/she/they) listens.

Formation (simplified):

Verb: dinlemek – to listen
Aorist (simple present) 3rd person: dinler – he/she listens
Add the suffix -ken – while / when doing X
dinler + ken → dinlerken – while listening

The suffix -ken does not change with vowel harmony; it stays -ken.

Why isn’t there a separate o in dinlerken? How do I know who is doing the listening?

In dinlerken, the subject is understood to be the same as the subject of the main clause.

Main clause subject: O … not alıyor – He/She is taking notes
Time clause: dinlerken – while (he/she) is listening

Turkish often “shares” the subject between a main clause and clauses with -ken, so you do not repeat o inside dinlerken.

What does not alıyor literally mean? Why is almak used?

not alıyor literally is is taking note(s).

not – note, borrowed from European languages
almak – to take
alıyor – is taking / takes

Turkish often uses a noun plus a light verb like almak to form a single meaning. not almak is the standard way to say to take notes.

Why doesn’t not have an -ı/-i ending? Why not notu alıyor?

In Turkish, the direct object is marked with -(y)ı / -(y)i / -(y)u / -(y)ü (accusative) when it is specific or definite.

not alıyor – he takes notes (in general; non‑specific notes)
notu alıyor – he is taking the note or he is taking that specific note

Here we are talking about note‑taking as a general habit, so not stays unmarked: not alıyor.

Why is alıyor used (present continuous) instead of alır (aorist)? Isn’t this a habitual action?

Both tenses can describe habits, but they feel different:

not alıyor – often used for a current, typical, or characteristic behavior, especially in spoken Turkish: He takes notes (as something he tends to do).
not alır – more like a general fact or rule: He takes notes (as a rule, generally speaking).

In everyday speech, -yor is very common even for repeated or typical actions, especially when you are describing a person’s characteristic way of doing things. That is why not alıyor sounds very natural here.

What does bu yüzden mean, exactly? Can I use something else instead?

bu yüzden literally means for this reason or because of this and is used like so / therefore.

Similar expressions:

bu yüzden – for this reason, so
bu nedenle / bu sebeple – very similar, a little more formal
o yüzden – for that reason, so

They can usually replace each other without changing the basic meaning: … not alıyor, bu yüzden / bu nedenle / o yüzden daha iyi hatırlıyor.

How does daha iyi work here? Where is the word for better?

Turkish forms the comparative with daha placed before an adjective or adverb.

iyi – good / well
daha iyi – better (literally more good / more well)

So daha iyi hatırlıyor means he remembers better or he remembers more well. The word order is fixed: daha comes right before iyi.

What is the nuance of hatırlıyor here? Is it is remembering or remembers?

Formally, hatırlıyor is present continuous (is remembering), but in a sentence like this it is best translated as remembers.

daha iyi hatırlıyor – he remembers better / he has a better memory (as a result)

As with alıyor, the -yor tense is often used for general tendencies or characteristic behavior, not only for actions happening right now.

Could I say dinlediğinde not alıyor instead of dinlerken not alıyor? What is the difference?

Both are possible, but there is a nuance:

dinlerken not alıyor – He takes notes while (he is) listening.
- Focus on simultaneity: the two actions are happening at the same time.
dinlediğinde not alıyor – When he listens, he takes notes.
- Focus on whenever or when he listens; sounds a bit more like a rule or repeated event linked to a time point.

In your sentence, dinlerken is slightly more natural because note‑taking clearly happens during listening.