Ο καρπός μου πονάει όταν γράφω πολλή ώρα.

Yes. καρπός has more than one meaning in Greek.

In everyday language, ο καρπός can mean:

• fruit
• wrist

Usually the context makes it clear:

• Ο καρπός είναι ώριμος. = The fruit is ripe.
• Ο καρπός μου πονάει. = My wrist hurts.

This is very normal in Greek, even if it feels surprising at first.

ο is the masculine singular definite article, meaning the.

Greek usually uses the definite article much more often than English, especially with:

• body parts
• possessive expressions
• general nouns in ordinary statements

So Ο καρπός μου literally looks like the wrist my, but it means my wrist.

This pattern is extremely common:

• το χέρι μου = my hand
• το πόδι μου = my leg
• ο λαιμός μου = my neck

In Greek, the article is not optional here.

Because in Greek, weak possessive forms like μου usually come after the noun.

So:

• ο καρπός μου = my wrist
• το βιβλίο μου = my book
• η φίλη μου = my friend

This is different from English, where my comes before the noun.

A useful way to think of it is:

• μου = of me / my

So ο καρπός μου is literally something like the wrist of me, although you should translate it simply as my wrist.

Because the subject is ο καρπός μου = my wrist, which is singular.

So the verb agrees with wrist, not with me.

• Ο καρπός μου πονάει. = My wrist hurts.
• Οι καρποί μου πονάνε. = My wrists hurt.

Even though μου means my, it does not control the verb. The noun καρπός does.

These forms are related.

The dictionary form is commonly given as πονάω or πονώ = to hurt / to be in pain.

In the 3rd person singular, you may see:

• πονάει
• πονά

Both are common in Modern Greek.

So these are both fine:

• Ο καρπός μου πονάει.
• Ο καρπός μου πονά.

πονάει often sounds a bit more explicit/full, while πονά is also very natural and common.

You may also encounter forms from the more formal pattern, but for everyday speech, πονάω / πονάει / πονά are the most useful to know.

Because this sentence describes something that happens whenever or when the speaker writes for a long time.

In Greek, όταν is often followed by the present tense for repeated or general situations:

• Όταν γράφω πολλή ώρα, ο καρπός μου πονάει.
• Όταν διαβάζω πολύ, κουράζομαι.
• Όταν τρέχει, γλιστράει ο δρόμος.

Here, γράφω means I write / I am writing, depending on context.

So the sentence means something like:

• My wrist hurts when I write for a long time
• or Whenever I write for a long time, my wrist hurts

Because the person doing the writing is I.

The sentence has two parts:

• Ο καρπός μου πονάει = My wrist hurts
• όταν γράφω πολλή ώρα = when I write for a long time

Greek often leaves out the subject pronoun εγώ because the verb ending already shows who the subject is.

So:

• γράφω = I write
• γράφεις = you write
• γράφει = he/she/it writes

There is no need to say εγώ γράφω unless you want emphasis.

Because ώρα is a feminine noun.

The word πολύς / πολλή / πολύ changes form to agree with the noun:

• πολύς for masculine
• πολλή for feminine
• πολύ for neuter

Since ώρα is feminine, Greek uses πολλή:

• πολλή ώρα = a long time
• πολλή δουλειά = a lot of work
• πολλή ζέστη = a lot of heat

Compare:

• πολύ νερό = a lot of water (neuter)
• πολλός κόσμος = a lot of people / a big crowd (masculine)

So πολλή ώρα is the correct agreement.

Here πολλή ώρα means for a long time.

This is a very common Greek expression. Greek often uses it without a separate word for for in this kind of time expression.

So:

• γράφω πολλή ώρα = I write for a long time
• περίμενα πολλή ώρα = I waited a long time
• μιλούσαμε πολλή ώρα = we were talking for a long time

It does not necessarily mean many hours literally. It usually just means a long time.

Yes, that is also very natural Greek.

You can say:

• Ο καρπός μου πονάει.
• Με πονάει ο καρπός μου.

Both mean My wrist hurts.

The second version literally includes με = me, so it is closer to My wrist is hurting me. Greek often uses this pattern with body pain:

• Με πονάει το κεφάλι μου. = My head hurts.
• Με πονάει η μέση μου. = My lower back hurts.

Both structures are common, and the choice is often about style, emphasis, or what sounds most natural in the moment.

Because the Greek present tense often covers both:

• simple present: I write
• present progressive: I am writing

So:

• γράφω can mean I write or I am writing
• πονάει can mean it hurts or it is hurting

The exact meaning comes from context.

In this sentence, the idea is general and repeated, so English often translates it with the simple present:

• My wrist hurts when I write for a long time.

But depending on context, English could also phrase it progressively:

• My wrist starts hurting when I’ve been writing for a long time.

Greek does not need a separate -ing form the way English does.