Learn Hardcore Turkish: Zihnim yorgunken uzun metinleri okuyamıyorum. - When my mind is tired, I cannot read long texts.

Turkish has vowel drop (ünlü düşmesi) in some two-syllable nouns when a vowel-initial suffix is added. Zihin + 1sg possessive -(I)m would be zihinim, but the second vowel of the root drops: zihnim.

Pattern: zihin + -im → zihinim → zihnim
Other examples: burun → burnum (my nose), ağız → ağzım (my mouth)

You don’t need benim because the possessive suffix already marks “my.” Benim zihnim is only for emphasis or contrast.

What does -ken in yorgunken mean, and when do I use -ken vs -yken?

-ken means “while/when (during the time that).” It attaches to adjectives, nouns, adverbs, and verb stems.

After a consonant: just -ken → yorgun
- -ken → yorgunken (while tired)
After a vowel: insert buffer y → evde
- -yken → evdeyken (while at home)
With verbs: oku
- -rken (historically from -iken) → okurken (while reading)

Can I say yorgun iken or yorgun olunca instead of yorgunken? Are they the same?

yorgunken and yorgun iken are equivalent in meaning (“while/when [being] tired”). Yorgunken is the standard fused form; yorgun iken looks more formal/literary.
yorgun olunca leans toward “when/once I become tired,” focusing on the moment/condition of becoming tired rather than the ongoing state. In many contexts it still works close to “when tired.”

Why is the object uzun metinleri in the accusative? Should it be uzun metinler?

Accusative -(y)i marks a definite/specific direct object.

uzun metinleri okuyamıyorum = I can’t read the long texts (that we have/that I have in mind).
If you mean “I can’t read long texts (in general),” drop the accusative: uzun metinler okuyamıyorum (or singular mass-like: uzun metin okuyamıyorum).

So choose accusative only if those texts are specific to the discourse.

What’s the difference between okuyamıyorum and okumuyorum?

okuyamıyorum = “I can’t read / I am unable to read” (inability: mental, physical, circumstantial).
okumuyorum = “I am not reading” (simple negation of the action, not necessarily inability).

Here, with a cause like “my mind is tired,” okuyamıyorum is the natural choice.

How is okuyamıyorum built? Why the buffer y and why a (not e)?

Breakdown: oku (read) + potential negative -A-mA- + progressive -yor + -um (1sg)

Form: oku + (y)A + mA + yor + um → oku-ya-ma-yor-um → okuyamıyorum
The buffer y prevents vowel clash (oku + a → okuya-).
Vowel harmony: the variable vowel -A-/-E- surfaces as -a- here because the last vowel of oku- is back (u). Likewise, the negative -mA- uses a after a back vowel.

Affirmatives: “I can read” can be either okuyabilirim (general ability) or okuyabiliyorum (I’m able to read [now]).

Should it be okuyamıyorum or okuyamam with this time clause?

Both are correct; they differ in aspect:

okuyamıyorum (progressive) = I can’t read (right now/at this time).
okuyamam (aorist) = I can’t read (as a rule, whenever that condition holds).

With a general condition like “when my mind is tired,” okuyamam often fits better for a habitual statement:

Zihnim yorgunken uzun metinleri okuyamam.

Can I drop zihnim and just say Yorgunken uzun metinleri okuyamıyorum?

Yes. With adjectives + -ken, the unexpressed subject defaults to the main clause subject. Yorgunken alone means “when I am tired.” Adding zihnim narrows the meaning to “when my mind is tired,” which is more precise than general tiredness.

Could I use zihnim yorgun olduğunda instead of zihnim yorgunken?

Yes. … olduğunda literally means “when it is …,” and it’s perfectly natural:

Zihnim yorgun olduğunda uzun metinleri okuyamıyorum/okuyamam. Nuance:
… yorgunken is a bit more compact and feels like “while (being) tired.”
… yorgun olduğunda is slightly more explicit/formal but very common.

Where can I place the time clause in the sentence?

Turkish word order is flexible. Common options:

Zihnim yorgunken uzun metinleri okuyamıyorum. (Time clause first = neutral)
Uzun metinleri, zihnim yorgunken okuyamıyorum. (Object fronted for focus)
Uzun metinleri okuyamıyorum, zihnim yorgunken. (End position for afterthought/emphasis)

The verb typically stays last; moving constituents changes emphasis, not core meaning.

Can -ken attach to verbs too, like “while reading”?

Yes. With verbs, it appears as -rken (from historical -iken):

okurken = while reading
You can combine conditions: Zihnim yorgunken, (uzun) metinleri okurken zorlanıyorum.

Is writing yorgun iken as two words acceptable, or must it be fused?

Both are acceptable. The fused form (yorgunken / evdeyken / okurken) is by far more common in modern usage. The spaced form (yorgun iken) looks more formal or literary.