Zehir balığı öldürdü.

Because neutral Turkish word order is often Subject + Object + Verb.

So in Zehir balığı öldürdü:

• zehir = subject
• balığı = object
• öldürdü = verb

English usually prefers Subject + Verb + Object, so this feels reversed to English speakers.

We know because balığı has the accusative ending -ı, which marks it as a definite/specific direct object.

So:

• zehir = the thing doing the action
• balığı = the thing affected by the action

Turkish often relies on case endings like this more than English does.

The base word is balık. Here it takes the accusative ending because it is a definite/specific direct object.

So:

• balık = fish
• balığı = the fish / fish as a marked direct object

In Turkish, a direct object is often marked with the accusative when it is definite or specific.

This is a common sound and spelling change in Turkish.

When some words ending in k take a vowel-initial suffix, the k often softens to ğ.

So:

• balık
• balık + ı
• becomes balığı

This is normal and something you will see a lot in Turkish.

Öldürdü comes from öldürmek, which means to kill.

It can be understood as:

• öldür- = kill
• -dü = past tense

So öldürdü means killed or more literally he/she/it killed.

Turkish does not need a separate subject pronoun here, because the sentence already has zehir as the subject.

Yes.

• ölmek = to die
• öldürmek = to kill

So öldürmek is basically the causative form: to make die.

This is a very useful pattern in Turkish, because many verbs can form a causative version.

Turkish does not have a separate word like English the.

Instead, definiteness is often understood from:

• context
• word order
• case marking

In this sentence, the accusative ending on balığı helps show that the object is definite/specific, which is why it matches English the fish.

Without the accusative ending, the object would usually sound more indefinite or non-specific.

So the difference is roughly:

• balığı = the fish / a specific fish
• balık = fish / a fish in a less specific sense

This definite-vs.-indefinite object distinction is very important in Turkish.

The ğ in Turkish is usually not pronounced like a hard English g.

In balığı, it usually:

• lengthens the previous vowel a little, or
• creates a very slight glide

Also, both ı letters are dotless i, which is a Turkish vowel English does not have.

So balığı should not sound like baligi. The ğ is very soft, and the ı is a back vowel.

Yes. Turkish word order is flexible, because case endings help show who is doing what.

For example, Balığı zehir öldürdü still has the same basic meaning, but the focus changes. It can sound more like:

• It was the poison that killed the fish

So Zehir balığı öldürdü is the more neutral order, while other orders can add emphasis or focus.