Dün parkta koşarken bileğim ağrıdı.

Parkta is park + -ta, the locative ending, meaning in the park or at the park.

• park = park
• -ta / -te / -da / -de = in / at / on, depending on vowel harmony and consonant voicing

Here, park ends in the voiceless consonant k, so the suffix appears as -ta rather than -da.

So:

• park = park
• parkta = in the park

Koşarken comes from the verb koşmak (to run).

It is built from the verb stem koş- plus -arken, which means while doing or when doing.

So:

• koşmak = to run
• koş- = run
• koşarken = while running

This form shows that one action was happening at the same time as another. In this sentence, the wrist started hurting during the time the speaker was running.

Both can mean while running, but koşarken is the more common and natural form here.

• koşarken = while running
• koşuyorken = while (I/he/she/etc.) was running

Very roughly:

• koşarken is shorter and more general
• koşuyorken sounds more explicit and can feel heavier

In everyday Turkish, koşarken is very normal for this kind of sentence.

Because Turkish usually marks body parts with a possessive suffix when they belong to someone.

• bilek = wrist
• bileğim = my wrist

The -im / -ım / -üm / -um type suffix means my, depending on vowel harmony.

So Turkish often says:

• başım ağrıyor = my head hurts
• kolum kırıldı = my arm broke
• bileğim ağrıdı = my wrist hurt

Using just bilek here would sound unnatural, because the sentence is talking about a specific person’s wrist.

This is a common sound change in Turkish.

Some words ending in k change that k to ğ when a vowel-starting suffix is added.

So:

• bilek
  • -im → bileğim

This happens in many words:

• kulak → kulağım = my ear
• ayak → ayağım = my foot
• renk → rengim = my color

So bileğim is the expected form, not an irregular one you just have to memorize separately.

Because the possessive suffix on the noun already gives that meaning.

• bileğim already means my wrist

So benim is not necessary.

You could say benim bileğim, but that usually adds emphasis, such as:

• Benim bileğim ağrıdı, onunki değil.
  My wrist hurt, not his/hers.

In a neutral sentence, just bileğim is enough.

Ağrıdı comes from the verb ağrımak, which means to ache / to hurt.

• ağrımak = to ache, to hurt
• ağrıdı = hurt / ached

In this sentence, bileğim ağrıdı means my wrist hurt or my wrist started hurting.

This verb is commonly used for pain in body parts:

• Başım ağrıyor. = My head hurts.
• Dişim ağrıdı. = My tooth hurt.

The ending -dı / -di / -du / -dü is the simple past tense in Turkish.

So:

• ağrıyor = is hurting / hurts
• ağrıdı = hurt / started hurting

Because the sentence includes dün (yesterday), the past tense is the natural choice.

It can suggest either, depending on context, but very often ağrıdı is understood as it hurt or it started hurting at that time.

So in this sentence, a natural interpretation is:

• Yesterday, while I was running in the park, my wrist started hurting.

If the speaker wanted to emphasize an ongoing state more clearly, Turkish might use a different form, such as ağrıyordu in another context.

Turkish often leaves pronouns out when they are understood from context.

Here, the sentence does not explicitly say I, but it is understood because of:

• bileğim = my wrist
• the overall meaning of the sentence

Turkish does this a lot. It is very normal not to state ben unless there is emphasis or contrast.

Dün means yesterday and gives the time of the event.

It does not have to come first, but sentence-initial position is very common because Turkish often puts time expressions near the beginning.

For example, all of these are possible:

• Dün parkta koşarken bileğim ağrıdı.
• Parkta dün koşarken bileğim ağrıdı.
• Bileğim dün parkta koşarken ağrıdı.

The first one is the most neutral and natural.

No, Turkish word order is fairly flexible, but the chosen order sounds natural and clear.

Here the sentence is organized roughly like this:

• Dün = time
• parkta = place
• koşarken = background action
• bileğim = subject/topic
• ağrıdı = main verb

Turkish often places the main verb at the end. The words before it can move around, but changing the order can change emphasis.

Because koşarken gives the background situation for the main event.

The structure is basically:

• While running in the park yesterday, my wrist hurt.

So:

• koşarken = background / simultaneous action
• ağrıdı = main event

This is a very common Turkish pattern: first the circumstance, then the main action.

By itself, koşarken does not mark person, so technically it can mean while running without saying who was running.

But in this sentence, the most natural interpretation is that the owner of the wrist and the runner are the same person, especially because of bileğim (my wrist).

So learners normally understand it as:

• While I was running, my wrist hurt.

If Turkish wanted to make a different subject clearer, it would usually add more information.

That is a very useful comparison.

• koşarken = while running
• koştuğumda = when I ran / when I was running

Koşarken focuses more on the action being in progress at the same time as the pain.

Koştuğumda can sound more like when I ran in a broader sense, not always emphasizing the ongoing overlap as strongly.

So for simultaneous background action, koşarken is especially natural here.

Yes, very common.

Turkish often uses:

• [body part + possessive] + ağrımak

Examples:

• Başım ağrıdı. = My head hurt.
• Dizim ağrıyor. = My knee hurts / is hurting.
• Omzum ağrıdı. = My shoulder hurt.

So bileğim ağrıdı fits a very common Turkish pattern for describing pain in a body part.