Learn Hardcore Turkish: Çarşaf pek temiz değil, şimdi onu değiştiriyorum. - The bedsheet isn’t very clean; I’m changing it now.

Çarşaf primarily means bed sheet (the sheet you spread on a mattress). In other contexts, çarşaf can also refer to a full-body outer garment some women wear (context will make this clear). Related bedding words:

nevresim: duvet/comforter cover
yastık kılıfı: pillowcase
yorgan: duvet/comforter
örtü: cover/throw

Why is pek used here, and what nuance does it add?

With a negative, pek means not very. So pek temiz değil means not very clean. It softens the criticism a bit. Notes:

pek in positive sentences (like pek güzel) is formal/old-fashioned in everyday speech, though it’s fine in writing.
pek çok (many, a lot of) is very common: pek çok insan (many people).
Alternatives:
- çok temiz değil ≈ not very clean (common, neutral).
- fazla temiz değil ≈ not too clean (often a touch more negative or colloquial depending on tone).

How does pek temiz değil compare to hiç temiz değil?

pek temiz değil: not very clean (mild).
hiç temiz değil: not clean at all (stronger, categorical).
You could also say kirli (dirty) if you want to be direct.

Why is değil used instead of a verb for be?

Turkish doesn’t use a stand-alone verb for be in the present for nominal/adjectival sentences. You say Çarşaf temiz (The sheet is clean) with no verb. To negate such sentences, Turkish uses değil: Çarşaf temiz değil (The sheet is not clean).

Why doesn’t değil have a personal ending here?

With a third-person singular subject like çarşaf, you normally don’t add a personal suffix to değil: temiz değil. For other persons, değil takes personal endings:

Ben temiz değilim
Sen temiz değilsin
O temiz değil
Biz temiz değiliz
Siz temiz değilsiniz
Onlar (human) temiz değiller; for inanimate plurals, both değil and değiller are heard (see below).

What does onu mean here, and why the final -u?

Onu is the accusative (direct object) form of o (he/she/it), so onu means him/her/it as a definite object. You use the accusative when the object is specific/definite. The -n- is a buffer that third-person pronouns take before case endings: o → onu (accusative), onun (genitive).

Here, onu refers back to çarşaf (it).
You could also say çarşafı değiştiriyorum (I’m changing the sheet). The -ı on çarşafı is the accusative, again marking definiteness.
If the object were indefinite, you would not use the accusative: çarşaf değiştiriyorum (I’m changing a sheet).

Can I omit onu?

Yes. If context makes the object clear, Şimdi değiştiriyorum is fine. Including onu just makes the reference explicit or adds focus to the object. Using çarşafı instead of onu is also fine and a bit more explicit.

Is onun ever correct here instead of onu?

No. Onun is genitive (his/her/its), not a direct object. You need the accusative onu for I’m changing it.

How flexible is the word order in Şimdi onu değiştiriyorum?

Turkish is quite flexible, but the neutral order places the object before the verb. Common variants:

Şimdi onu değiştiriyorum (neutral, with time adverb first)
Onu şimdi değiştiriyorum (slightly more focus on the object)
Onu değiştiriyorum şimdi (afterthought/colloquial feel) In general, the element right before the verb tends to be the focus.

What’s inside the verb değiştiriyorum?

It’s built from:

değiş (change) + causative -tir (make something change) → değiştir- (to change something)
present continuous -iyor (harmonized as -ıyor/-iyor/-uyor/-üyor)
1st person singular -um Altogether: değiş-tir-iyor-um → değiştiriyorum (I am changing).

Why present continuous (-iyor) and not future (değiştireceğim)?

With şimdi (now), the present continuous is the natural choice: it describes an action in progress. If you say Şimdi onu değiştireceğim, it sounds like a near-future intention or promise (I’m about to change it / I will change it now), not that you’re already doing it.

What’s the difference between değişmek and değiştirmek?

değişmek: to change (intransitive; something changes by itself). Example: Hava değişiyor (The weather is changing).
değiştirmek: to change something (transitive; you cause the change). Example: Çarşafı değiştiriyorum (I’m changing the sheet).

Could I say Çarşafı pek temiz değil?

That would usually be understood as His/Her sheet isn’t very clean, because çarşafı is read as a possessed noun (çarşaf + 3rd-person possessive -ı) in subject position. To say The sheet isn’t very clean with no possessor, keep Çarşaf pek temiz değil.

How do plurals work here: Çarşaflar pek temiz değil or değiller?

Both occur in practice with inanimate plurals:

Çarşaflar pek temiz değil (very common)
Çarşaflar pek temiz değiller (also possible; the plural ending on değiller is more expected with human subjects, but it’s not strictly limited to them) With human subjects, değiller is strongly preferred: Öğrenciler burada değiller.