Learn Hardcore Turkish: Kesin değil, ama sanırım yarın boşum. - It’s not definite, but I think I’m free tomorrow.

boş-um = “I am free” (adjective + 1sg copula suffix).
değil negates nominal/adjectival predicates: kesin değil = “(it) is not certain.”
So the “am/is/are” meaning is carried by suffixes (like -um) or by değil for negation.

Why is it kesin değil and not something like kesin değilim?

Kesin değil is impersonal: “It’s not certain.” The implied subject is the situation, not “I.”
If you want to say “I’m not sure,” you’d say emin değilim (literally “I am not certain/sure”).

What exactly does sanırım mean and how is it formed?

It comes from sanmak “to suppose/assume.”
san-ır-ım = aorist/indefinite present + 1sg → “I suppose / I reckon.”
Nuance: it’s a soft, hedged opinion—less forceful than a direct assertion.

How does sanırım compare with sanıyorum, bence, galiba, and herhalde?

sanırım: “I suppose,” hedged, common in speech.
sanıyorum: literally “I am supposing”; close to sanırım, sometimes feels a shade more deliberate.
bence: “in my opinion,” more assertive.
galiba: “I guess,” often more tentative/guessy.
herhalde: “probably/most likely”; can range from tentative to fairly confident depending on tone.

What does boşum mean here? Is it the best word for “I’m free (available)”?

boş literally “empty,” but idiomatically “free/unoccupied.” boşum = “I’m free.”
It’s casual and common. In more formal or neutral contexts, müsaitim (“I’m available”) or uygunum (“I’m suitable/it works for me”) are preferred.

Why is the suffix in boşum “-um” and not something else?

Vowel harmony. The last vowel in boş is back and rounded (o), so the 1sg copula surfaces as -um: boş-um.
With front vowels you’d see -im/üm, with back unrounded -ım.

Can I change the word order? For example, can I say “Yarın sanırım boşum”?

Yes. All are possible with slight shifts in focus:

Sanırım yarın boşum. Neutral; the default.
Yarın sanırım boşum. Mild emphasis on “tomorrow” as the time frame.
Yarın boşum, sanırım. Adds a “hedge after the fact” vibe.
Avoid Boşum yarın unless you specifically want to emphasize “boşum” contrastively.

Why is there a comma before ama? Is it required?

It separates two clauses: “Not certain, but I suppose …”. In Turkish, placing a comma before ama is common and natural in such cases, though not absolutely mandatory.
Alternatives: fakat and ancak are more formal; ama is the everyday “but.”

Could I say the same idea without ama?

You could write two sentences or use a semicolon, but you would lose the explicit contrast that ama provides:

Kesin değil; sanırım yarın boşum. (works, slightly more formal)
Using ve (“and”) wouldn’t fit the “but/though” meaning.

Why not use yarına or yarın için?

yarın is an adverb meaning “tomorrow” and needs no suffix in “I’m free tomorrow.”
yarına or yarın için mean “for tomorrow”:
- Yarına boşum = odd (suggests “I am free for tomorrow” in a planning sense; better: yarın için).
- Yarın için uygunum/müsaitim = “I am available for tomorrow.”

How would I make the future time more explicit?

Use the future of “to be”:

Sanırım yarın boş olacağım. = “I think I will be free tomorrow.”
The original boşum already implies the state relevant to tomorrow, but olacağım makes the futurity explicit.

How can I say this more formally or in a professional message?

Henüz kesin değil; yarın müsait olabilirim.
Şu an net değil; yarın için uygun olma ihtimalim var.
Both hedge politely and sound professional.

How do I ask “Are you free tomorrow?” in Turkish?

Informal: Yarın boş musun? / Yarın müsait misin?
Polite/plural: Yarın boş musunuz? / Yarın müsait misiniz?

Any pronunciation tips for tricky letters here?

ğ in değil is a “soft g”: it lengthens/smooths the surrounding vowels; many speakers say something close to “deyil/diil,” not a hard “g.”
ı (dotless i) in sanırım is a back, unrounded vowel; it’s not the same as dotted i.