Learn Hardcore Turkish: Ben toplantıda not defteri kullanıyorum.

You can drop Ben. The verb kullanıyorum already marks first person singular. Ben is used for emphasis or contrast: Ben toplantıda not defteri kullanıyorum = It’s me who’s using a notebook.

What tense/aspect is kullanıyorum, and how is it different from kullanırım?

kullanıyorum is present continuous, used for right now or planned near future.
kullanırım is the aorist (habitual/generic), meaning I (usually) use.

Now: Şu anda toplantıda not defteri kullanıyorum.
Habit: Toplantılarda not defteri kullanırım.
Planned future: Yarın toplantıda not defteri kullanıyorum.

How is kullanıyorum formed?

Stem: kullan- (use)
Progressive: -ıyor (the high vowel is ı by vowel harmony because the last vowel in the stem is back a)
Person: -um (1st person singular)
Altogether: kullan-ıyor-um = kullanıyorum.

Why doesn’t not defteri have the accusative ending? Shouldn’t it be not defterini?

In Turkish, an indefinite direct object takes no accusative. not defteri is indefinite (a notebook). Use accusative only if it’s specific/definite:

Indefinite: Toplantıda not defteri kullanıyorum.
Definite: Toplantıda not defterini kullanıyorum. (the notebook)

What exactly does not defteri mean and how is it built?

It’s a noun–noun compound (belirtisiz isim tamlaması): not + defter-i (3rd person possessive on the second noun). Literally note-book, i.e., notebook.

Can I just say defter instead of not defteri?

Yes. defter on its own commonly means notebook. not defteri can sound a bit more specific (a notebook for notes/a notepad). Both are fine in everyday speech.

Why is it toplantıda and not toplantide or toplantita?

It’s the locative case -DA with vowel harmony and consonant voicing rules:

Last vowel of toplantı is back ı, so choose -da (not -de).
Because the stem ends in a vowel, the suffix-initial consonant stays voiced d (not t).
Result: toplantı + da → toplantıda.

Can I move the words around, or is the given order required?

Turkish prefers S-(time/place)-O-V, but you can move constituents for emphasis as long as the verb stays last:

Neutral: Toplantıda not defteri kullanıyorum.
Emphasis on place: Not defteri toplantıda kullanıyorum.
Avoid placing the verb before the object in simple statements.

Should I add bir before not defteri?

Not necessary. Without bir, it’s already an indefinite object. Adding bir can highlight newness or quantity: Toplantıda bir not defteri kullanıyorum (I’m using a notebook, one notebook).

How do I say at my meeting / at his meeting?

Add possessive before the locative:

toplantımda = at my meeting
toplantımızda = at our meeting
toplantısında = at his/her meeting

How do I make this negative or turn it into a yes–no question?

Negative: Toplantıda not defteri kullanmıyorum.
Question: Toplantıda not defteri kullanıyor muyum?
Note the separate question particle mi/mı/mu/mü with vowel harmony: kullanıyor mu-y-um?

How do I pronounce the dotless ı in toplantıda and kullanıyorum?

Turkish ı (dotless) is a close back unrounded vowel, like the second sound in English “roses.”

toplantıda ≈ tohp-lahn-tuh-DA
kullanıyorum ≈ kool-lahn-uh-YO-room

Is there a more natural way to say I’m taking notes at the meeting?

Yes, idiomatic options:

Toplantıda not tutuyorum.
Toplantıda not alıyorum.
Both mean I’m taking notes (rather than emphasizing the tool).

How do I express a general habit across meetings?

Use the aorist and often the plural: Toplantılarda not defteri kullanırım (In meetings, I use a notebook).

What’s the difference between toplantıda and toplantı için?

toplantıda = at/in the meeting (location/time).
toplantı için = for the meeting (purpose).
So Toplantı için not defteri kullanıyorum means I’m using a notebook for the meeting’s sake/preparation.

Is da here the same as the separate word de/da meaning also?

No. In toplantıda, -da is a locative suffix, written attached and can surface as -de/-da/-te/-ta. The particle de/da meaning also is written separately and never becomes te/ta:

Ben de toplantıda not defteri kullanıyorum. (I also use a notebook at the meeting.)