Bütün gün oturunca belim ağrıyor.

Bütün gün means all day or the whole day.

• bütün = whole, entire, all
• gün = day

So bütün gün oturunca is literally something like when/after sitting the whole day.

Turkish often uses bütün + time word this way:

• bütün gece = all night
• bütün hafta = all week

Oturunca comes from the verb oturmak (to sit, sometimes to sit down, depending on context).

It is formed like this:

• otur- = verb stem
• -unca / -ince = a suffix meaning when, once, after, or sometimes whenever

So oturunca can mean:

• when (someone) sits
• when I sit
• after sitting
• whenever (someone) sits

In this sentence, it gives the idea: When/if I sit all day, my lower back hurts.

Because Turkish often leaves the subject understood from context, oturunca does not have to explicitly say I.

Turkish often drops subject pronouns when they are already clear from context.

In this sentence, the idea of I / my is understood mainly because of belim:

• bel = lower back / waist
• belim = my lower back

So once Turkish says belim, it is already clear that the speaker is talking about themself.

You could say Ben bütün gün oturunca belim ağrıyor, but ben is usually unnecessary unless you want emphasis.

Because Turkish usually uses a possessive ending for body parts when talking about your own body.

• bel = lower back / waist
• belim = my lower back

The ending -im here means my.

This is very common in Turkish:

• başım ağrıyor = my head hurts
• kolum ağrıyor = my arm hurts
• ayağım ağrıyor = my foot hurts

So belim ağrıyor literally means my lower back hurts / my lower back is aching.

Ağrıyor comes from ağrımak, which means to hurt, to ache, or to be painful.

The form ağrıyor is the present continuous form, but in Turkish this tense is also often used for:

• things happening now
• repeated situations
• general personal experiences

So belim ağrıyor can mean:

• My back is hurting
• My back hurts
• My back aches

In English we might use the simple present (hurts) for a general pattern, but Turkish very naturally uses -yor here.

Because the grammatical subject of the verb is not I. The subject is belim (my lower back).

So the structure is:

• belim = my lower back
• ağrıyor = hurts / is aching

Literally: My lower back hurts.

The verb agrees with belim, which is third person singular grammatically, not with the owner of the back.

This works the same way in many Turkish body-pain sentences:

• Başım ağrıyor = My head hurts
• Dişim ağrıyor = My tooth hurts

It can suggest several of those meanings depending on context. That is one reason learners find it tricky.

In this sentence, oturunca most naturally means something like:

• when I sit all day
• if I sit all day
• after sitting all day
• whenever I sit all day

Because the rest of the sentence describes a repeated or typical result (belim ağrıyor), the overall meaning is close to:

When/if I sit all day, my lower back hurts.

So -ınca/-ince often connects one action or condition to a result.

Usually it sounds like a general result or repeated experience:

If/when I sit all day, my lower back hurts.

That comes from the combination of:

• oturunca = when/if/whenever sitting
• ağrıyor = hurts / is hurting

Depending on context, it could describe the present situation too, but without extra context most learners should understand it as a general personal statement.

Not exactly.

• bel usually means the waist or lower back
• sırt usually means the back, especially the upper/back area

So:

• Belim ağrıyor = My lower back hurts / My waist area hurts
• Sırtım ağrıyor = My back hurts

In this sentence, belim is more specifically my lower back.

Yes, you could, and it is very close in meaning.

• Bütün gün oturunca belim ağrıyor.
• Bütün gün oturursam belim ağrır.

A rough difference:

1. -ınca version
   Bütün gün oturunca belim ağrıyor.
   = When/if I sit all day, my back hurts.
   This can sound more like a natural, experience-based result.

2. -sA conditional version
   Bütün gün oturursam belim ağrır.
   = If I sit all day, my back hurts/will hurt.
   This sounds a bit more explicitly conditional.

Both are natural. The original sentence feels very conversational and common.

The given word order is natural and neutral, but Turkish word order is somewhat flexible.

The basic idea is:

• Bütün gün oturunca = when/if after sitting all day
• belim ağrıyor = my lower back hurts

This order is very normal because the condition comes first and the result comes second.

Turkish often puts background information before the main statement. So this sentence flows naturally as:

[condition] + [result]

Because Turkish usually expresses possession with a suffix instead of a separate word.

In English:

• my back

In Turkish:

• bel-im

That -im already means my.

So Turkish does not need a separate word like my here. The possessive idea is built into the noun itself.

That is why:

• belim = my lower back
• elim = my hand
• gözüm = my eye