Köpeğin su kabı boş.

Because köpeğin is the genitive form of köpek (dog), and it means of the dog or the dog's.

• Base noun: köpek
• Genitive ending: -(n)in / -(n)ın / -(n)un / -(n)ün
• Here: köpek + in → köpeğin

The final k changes to ğ before the vowel-initial ending, so köpek becomes köpeğin.

So:

• köpek = dog
• köpeğin = the dog's / of the dog

Because su kabı is a noun compound meaning water bowl/container.

In Turkish, when one noun describes another noun in this kind of possessive-style compound, the second noun usually takes the third-person possessive ending.

So:

• su = water
• kap = container, bowl, vessel
• su kabı = water bowl / bowl for water

This is a very common structure in Turkish:

• çay bardağı = tea glass
• kapı kolu = door handle
• diş fırçası = toothbrush

So su kabı is not literally just water + bowl placed side by side in the English way; it follows a regular Turkish compound pattern.

This is a very common Turkish pattern called a genitive-possessive construction.

It works like this:

• the owner gets the genitive ending
• the thing owned gets a possessive ending

So in köpeğin su kabı:

• köpeğin = of the dog / the dog's
• su kabı = its water bowl / water bowl

Together, this gives the dog's water bowl.

You can think of the structure as:

[owner + genitive] + [owned thing + possessive]

Examples:

• adamın arabası = the man's car
• evin kapısı = the door of the house
• kedinin oyuncağı = the cat's toy

In Turkish, in simple present-tense sentences like this one, the verb to be is often not expressed in the third person.

So:

• Köpeğin su kabı boş. = The dog's water bowl is empty.

There is no separate word for is here, but the meaning is complete and natural.

This is very common:

• Hava güzel. = The weather is nice.
• Ev büyük. = The house is big.
• Su soğuk. = The water is cold.

You may also see boştur, which is more formal or emphatic:

• Köpeğin su kabı boştur.

But in everyday speech, boş by itself is normal.

Because in Turkish, the predicate often comes at the end of the sentence.

Here:

• Köpeğin su kabı = the dog's water bowl
• boş = empty

So the sentence structure is basically:

subject + predicate

Turkish often puts descriptive words before nouns when they directly modify them, but here boş is not directly modifying the noun inside a noun phrase like empty bowl. Instead, it is the main predicate of the sentence:

• su kabı = water bowl
• boş su kabı = empty water bowl
• su kabı boş = the water bowl is empty

That difference is important.

In this sentence, it most naturally means the dog's water bowl or the water bowl of the dog.

Turkish does not have articles like the and a, so definiteness is often understood from the structure and context.

The genitive-possessive construction usually sounds fairly specific:

• köpeğin su kabı = the dog's water bowl

Without context, English may sometimes translate it in different ways, but the dog's water bowl is the most natural interpretation.

Because Turkish does not use articles the way English does.

English requires words like:

• a
• an
• the

Turkish usually does not.

So:

• köpek can mean dog, a dog, or the dog, depending on context.
• su kabı can mean water bowl or the water bowl, depending on context.

The sentence is understood through grammar and situation, not articles.

Because su kabı is a standard Turkish noun compound.

The clue is the ending on the second noun:

• kap = bowl/container
• kabı = its bowl/container

That possessive ending shows that the two nouns are linked as a compound.

So su kabı means something like:

• bowl for water
• water bowl
• water container

It works as a single unit inside the larger phrase:

• köpeğin [su kabı] boş

Here, boş means empty.

It is a very common adjective and can also mean things like:

• empty
• vacant
• unoccupied
• free/available
• pointless, depending on context

But in Köpeğin su kabı boş, the meaning is clearly empty because it describes the state of the dog's water bowl.

In köpeğin, the letter ğ is usually not pronounced like a strong consonant in modern Turkish.

A rough pronunciation is:

• kö-pe-in or kö-pe-yin, depending on speech flow

The ğ often:

• lengthens the preceding vowel, or
• creates a smooth transition between vowels

So you should not pronounce it like a hard g in English.

Very roughly:

• köpek ≈ kur-peck with rounded vowels
• köpeğin ≈ kur-peh-een with a soft transition

The exact sound depends on accent and speed, but the important thing is: ğ is soft, not a hard g.

Yes, you could.

• Köpeğin su kabı boş. = normal, everyday
• Köpeğin su kabı boştur. = more formal, more definite, sometimes more emphatic

The ending -dır / -dir / -dur / -dür / -tır / -tir / -tur / -tür can add a sense of assertion, formality, or general statement.

In casual speech, people usually just say:

• Köpeğin su kabı boş.

That would be a noun phrase, not a full sentence.

• Köpeğin su kabı boş. = The dog's water bowl is empty.
• boş köpek su kabı would not be the natural equivalent here.

If you want to say the dog's empty water bowl, Turkish would usually say:

• köpeğin boş su kabı

Here, boş directly modifies su kabı inside the noun phrase.

Compare:

• köpeğin boş su kabı = the dog's empty water bowl
• köpeğin su kabı boş = the dog's water bowl is empty

That is a very useful distinction in Turkish.