Learn Hardcore Turkish: Yarın sabah bavul hazırlarken kontrol listesi kullanacağım. - Tomorrow morning, while packing my suitcase, I will use a checklist.

So -ken is essentially attached to the present-continuous stem and expresses a simultaneous action: one thing happens while another is in progress.

Why is there no subject pronoun ben (“I”) in the sentence?

In Turkish, the subject pronoun is usually dropped because it is already clear from the verb ending.

Verb: kullanacağım
- Root: kullan- (use)
- Future marker: -acak-
- 1st person singular: -ım

The -ım at the end tells you the subject is “I”, so ben is not needed.
Ben yarın sabah... kullanacağım is also correct, but ben is only used when you want to emphasize “I (as opposed to someone else)”.

How is kullanacağım built, and why does it have -acağım instead of -acakım or something else?

kullanacağım is the future tense, 1st person singular of kullanmak (to use).

Breakdown:

kullan- = verb root
-acak = future tense marker
-ım = “I” ending

So we theoretically get: kullan-acak-ım

Then two sound changes happen:

Final -k between vowels becomes -ğ: acakım → açağım
Vowel harmony and natural pronunciation give kullanacağım.

So kullanacağım = “I will use.”

What exactly does -ken add compared to a more explicit form like bavul hazırladığımda?

Both structures express time, but the nuance is a bit different:

bavul hazırlarken
= “while packing the suitcase” (focus on during / in the middle of the action; more “background” action)
bavul hazırladığımda
= literally “when I pack / when I have packed the suitcase”
This feels a bit more like a specific point in time.

In everyday speech, -ken is very common and sounds a bit lighter and more natural for “while doing X.”

How do we know that bavul hazırlarken means “while I am packing” and not “while someone else is packing”?

In Turkish, a -ken clause shares its subject with the main clause unless something else makes it clear.

Main clause subject: I (from kullanacağım)
No other subject is mentioned in bavul hazırlarken

So by default, bavul hazırlarken kontrol listesi kullanacağım is understood as:

“While I am packing the suitcase, I will use a checklist.”

If you wanted to say “while she is packing the suitcase, I will use a checklist”, you would have to express that explicitly, e.g. o bavul hazırlarken ben kontrol listesi kullanacağım.

Why is it kontrol listesi and not just kontrol liste?

Kontrol listesi is a noun–noun compound, which Turkish usually marks by adding a possessive ending on the second noun.

kontrol = control / check
liste = list
liste-si = “its list” → used as the second part of a compound

So:

kontrol listesi = literally “its control list” → idiomatically “checklist”

Without -si, kontrol liste sounds like “control list” said by a foreigner; it’s not how native speakers form this concept.

Why doesn’t kontrol listesi have an accusative ending like kontrol listesini?

In Turkish, a direct object gets the accusative -ı/-i/-u/-ü only when it is definite/specific.

kontrol listesi kullanacağım
= “I will use a checklist / checklists (in general)”
The object is non-specific / general.
kontrol listesini kullanacağım
= “I will use the (specific) checklist” (the one we already know about).

In your sentence, the idea is general—I’ll use a checklist (as a method)—so no accusative is used.

What is the role of bavul here, and why is it not marked with any case ending?

Bavul hazırlamak is a common collocation meaning “to pack (a suitcase)”.
Here, bavul is a direct object, but it is non-specific, so it is in the bare nominative form:

bavul hazırlıyorum = “I’m packing (a) suitcase.”
bavulu hazırlıyorum = “I’m packing the suitcase (you know which one).”

In bavul hazırlarken, it’s just the bare, non-specific form again. The sentence doesn’t emphasize one particular, known suitcase—just the activity of packing.

Can I say bavulu hazırlarken instead of bavul hazırlarken? What would change?

Yes, you can, but the meaning changes slightly:

bavul hazırlarken
= “while packing a suitcase / while packing (suitcases)” (non-specific)
bavulu hazırlarken
= “while packing the suitcase” (a specific, known suitcase)

The grammar is still correct in both. It’s just about whether the object is definite (add accusative -u) or indefinite/general (no ending).

Is the word order fixed, or can I move things around in this sentence?

Turkish is flexible with word order, but there is a natural preference:

Neutral, natural:
Yarın sabah bavul hazırlarken kontrol listesi kullanacağım.

You can move the time phrase around:

Bavul hazırlarken yarın sabah kontrol listesi kullanacağım. (still okay)

But you normally keep the verb at the end and don’t break the bavul hazırlarken block. Very unusual (and often wrong-sounding) would be something like:

✗ Yarın sabah bavul hazırlarken kullanacağım kontrol listesi.

So: time expressions can move, but “bavul hazırlarken” should stay together, and the verb kullanacağım should usually stay at the end.

Does yarın sabah have to be in that order? Can I say sabah yarın?

The natural expression is yarın sabah = “tomorrow morning.”

yarın sabah → correct, natural
sabah yarın → not used; sounds ungrammatical/very odd

You can also hear variants like:

yarın sabahleyin = tomorrow morning (a bit more “spoken”)
yarın sabah erken = tomorrow morning early

But the core order yarın sabah should stay as it is.