Pastanın üstüne üç mum koyduk, ama küçük kız dördüncüsünü de istemeden edemedi.

Pastanın üstüne means onto the top of the cake.

It breaks down like this:

• pasta = cake
• pastanın = of the cake
• üst = top, upper part
• üstü = its top / the top of it
• üstüne = onto its top

Turkish often uses words like üst in a possessive-style structure:

• pastanın üstü = the top of the cake
• pastanın üstüne = onto the top of the cake

The ending -e / -a is the dative, which often shows movement toward something. That is why üstüne fits with koymak here: the candles are being placed onto the cake.

A useful contrast:

• pastanın üstünde = on the cake / on top of the cake, already there
• pastanın üstüne = onto the cake / onto the top of the cake, movement toward it

After numbers, Turkish normally uses the noun in the singular.

So:

• üç mum = three candles
• not normally üç mumlar

This is one of the first big differences from English. In Turkish, the number already shows plurality, so the noun does not usually need a plural ending too.

The same pattern appears in:

• iki kitap = two books
• beş çocuk = five children
• on gün = ten days

It is built into the verb.

Koyduk breaks down as:

• koy- = put, place
• -du- = past tense
• -k = we

So koyduk means we put.

Turkish often leaves subject pronouns out because the verb ending already tells you the person:

• koydum = I put
• koydun = you put
• koydu = he/she/it put
• koyduk = we put

So there is no need to say biz koyduk unless you want extra emphasis on we.

Dördüncüsünü means the fourth one as a specific object.

It is built like this:

• dört = four
• dördüncü = fourth
• dördüncüsü = the fourth one
• dördüncüsünü = the fourth one, as the direct object

The ending that creates the fourth one is the -sı / -si / -su / -sü type ending. With ordinals and adjectives, Turkish often uses this to make a noun-like form:

• birincisi = the first one
• ikincisi = the second one
• dördüncüsü = the fourth one

Then the final -nü is the accusative ending, because it is a definite, specific direct object.

So dördüncüsünü is not just fourth. It is specifically the fourth one.

Yes.

The noun mum is understood from the earlier part of the sentence, so Turkish does not need to repeat it.

That is very natural in Turkish. Once the noun is clear, you can replace it with a form like dördüncüsü:

• üç mum koyduk = we put three candles
• dördüncüsünü de = the fourth one too / even the fourth one

A fuller version like dördüncü mumu da is possible, but dördüncüsünü de sounds smoother because mum has already been mentioned.

Here de means too, also, or sometimes even, depending on the tone.

So dördüncüsünü de means something like:

• the fourth one too
• also the fourth one
• even a fourth one

It is written separately because this de is a particle, not a regular suffix.

Compare:

• evde = in the house → this -de is a suffix, so it is attached
• ben de = me too → this de is a separate word, so it is written separately

In this sentence, de adds the idea that three candles were already there, but the girl wanted one more as well.

This is an idiomatic pattern.

-meden / -madan edememek means cannot help doing or cannot refrain from doing.

So:

• istemeden edemedi = she could not help wanting it
• in smoother English here: she couldn’t resist wanting a fourth one too
• depending on context, also: she just had to ask for a fourth one too

This pattern is best learned as a chunk:

• gülmeden edememek = cannot help laughing
• bakmadan edememek = cannot help looking
• sormadan edememek = cannot help asking

So istemeden edemedi is not meant to be translated word by word in a simple way. As a whole, it means she could not resist the desire.

By itself, istemeden often does mean without wanting to or unintentionally.

For example:

• Seni istemeden kırdım = I hurt you unintentionally

But in this sentence, istemeden is part of the fixed pattern istemeden edememek, so you should not interpret it separately in the usual way.

Here it does not mean that the girl wanted the fourth candle by accident. It means:

• she couldn’t help wanting it
• she couldn’t resist wanting it

So this is a good case where the whole expression matters more than the individual parts.

Yes, in form it feels a bit like a double negative, and that is one reason it confuses learners.

Literally, it looks like something close to:

• not wanting
• plus could not do

But together, -meden edememek has a positive idiomatic meaning:

• cannot help doing
• cannot refrain from doing

So the sentence does not mean the girl failed to want it. It means the opposite: she simply could not resist wanting it.

This is similar to how some expressions in other languages do not make sense if translated piece by piece. It is best to memorize -meden edememek as one structure.

Turkish normally puts the verb at the end, so the basic pattern is often:

• subject + object + verb

That is what you see here:

• küçük kız = the little girl
• dördüncüsünü de = the fourth one too
• istemeden edemedi = couldn’t help wanting it

So the second clause follows a very normal Turkish pattern.

English prefers:

• the little girl couldn’t resist wanting a fourth one too

Turkish prefers:

• the little girl the fourth one too couldn’t-help-wanting

That sounds strange in English, but it is natural in Turkish.

Turkish does not have articles like the and a / an.

Instead, definiteness is usually understood from:

• context
• word order
• case endings

For example:

• küçük kız can mean the little girl or a little girl, depending on context
• dördüncüsünü is clearly specific because of the accusative ending, so it means the fourth one

In this sentence, the context makes küçük kız naturally understood as the little girl, and dördüncüsünü is a definite object.

So Turkish often leaves English speakers asking where the is, but the language usually handles that idea without a separate word.