Ben gözlüğümü defterin üstüne koydum.

A natural word-by-word breakdown is:

• Ben = I
• gözlüğümü = my glasses / my eyeglasses (as the direct object)
• defterin = of the notebook / the notebook’s
• üstüne = onto the top of / on top of
• koydum = I put

So the sentence means something like:

• I put my glasses on top of the notebook.

A more structural breakdown would be:

• Ben = subject
• gözlüğümü = object
• defterin üstüne = location/direction phrase
• koydum = verb

Yes. In Turkish, the verb ending often already shows the subject.

• koydum = I put

So Ben is optional here. Turkish often drops subject pronouns when they are clear from the verb.

That means both of these are possible:

• Gözlüğümü defterin üstüne koydum.
• Ben gözlüğümü defterin üstüne koydum.

Adding Ben can give:

• emphasis
• contrast
• clarity

For example, Ben might suggest I put it there, not someone else.

Because gözlüğümü contains extra endings that mean my glasses and also mark it as the direct object.

It breaks down like this:

• gözlük = glasses / eyeglasses
• gözlüğüm = my glasses
• gözlüğümü = my glasses (as a definite direct object)

What changed?

1. Possessive suffix

   • -üm / -ım / -um / -im can mean my
   • So gözlük → gözlüğüm = my glasses

2. Accusative case

   • -ı / -i / -u / -ü marks a definite direct object
   • So gözlüğüm → gözlüğümü

There is also a consonant change:

• gözlük → gözlüğüm

This happens because the k softens to ğ before a vowel in many Turkish words.

This is a very common question for English speakers.

In Turkish, gözlük is the normal word for glasses / eyeglasses, even though it is not marked with the plural suffix -ler / -lar.

So:

• gözlük = glasses / a pair of glasses / eyeglasses

Turkish does not always match English in whether something is treated as singular or plural in form.

If needed, context tells you what kind of item is meant. In everyday use, gözlük normally means eyeglasses.

That final -ü is the accusative ending. Turkish often marks a specific/definite direct object this way.

Compare:

• gözlük koydum = I put glasses / I put a pair of glasses
• gözlüğümü koydum = I put my glasses

In this sentence, the object is very specific:

• not just any glasses
• my glasses

That is why the object appears with the accusative ending.

Because the sentence means movement onto the top of the notebook.

Let’s split it up:

• defterin = of the notebook
• üstü = its top / upper side
• üstüne = onto its top

So defterin üstüne literally works like:

• onto the notebook’s top

This is a very common Turkish pattern.

Compare:

• defterin üstüne koydum = I put it onto/on top of the notebook
• defterin üstünde = on top of the notebook, describing location
• deftere koydum = I put it into/on the notebook is not the right expression for on top of the notebook

So üstüne is used because the sentence describes motion toward that position.

This is an important distinction:

• üstüne = onto / on top of
  → usually shows direction or movement toward a place

• üstünde = on / on top of
  → usually shows location, where something already is

Examples:

• Kitabı masanın üstüne koydum.
  = I put the book onto the table.

• Kitap masanın üstünde.
  = The book is on the table.

In your sentence:

• defterin üstüne koydum

is correct because koymak involves placing something somewhere.

Because Turkish often uses a possessed construction with words like üst, alt, iç, ön, arka when talking about relative position.

So instead of saying something like:

• notebook top

Turkish says something closer to:

• the notebook’s top

That is why you get:

• defterin üstü = the top of the notebook
• defterin üstüne = onto the top of the notebook

This structure is extremely common:

• masanın üstünde = on the table
• kutunun içinde = in the box
• evin önünde = in front of the house

So defterin üstüne is the normal, idiomatic form.

koydum comes from the verb koymak, which means to put, to place, or to set.

Breakdown:

• koy- = verb stem
• -du- = past tense
• -m = I

So:

• koydum = I put

Because Turkish tense/person endings are built into the verb, one word can express what English needs several words to say.

Because Turkish normally follows Subject–Object–Verb order, unlike English, which is usually Subject–Verb–Object.

English:

• I put my glasses on the notebook.

Turkish:

• Ben gözlüğümü defterin üstüne koydum.
• literally: I my-glasses onto-the-notebook put

In Turkish, placing the verb at the end is the most neutral and standard pattern.

That said, Turkish word order is flexible, and changing it can affect emphasis.

Yes. Several suffixes change shape to match the vowels in the word they attach to. This is called vowel harmony.

For example:

• gözlük → gözlüğüm
• gözlüğüm → gözlüğümü
• üstü → üstüne
• koydum with -du rather than some other vowel form

Turkish suffixes often appear in different forms such as:

• -ı / -i / -u / -ü
• -da / -de / -ta / -te
• -a / -e

The choice depends mainly on the vowels, and sometimes also on whether the final consonant is voiced or voiceless.

So the endings in this sentence may look complicated, but they are following regular sound patterns.

Yes, often you can.

• defterin üstüne koydum
• defterin üzerine koydum

Both can mean I put it on top of the notebook.

A rough difference is:

• üstüne is very common and everyday
• üzerine can sound a little more formal or slightly more neutral depending on context

In many situations, they are interchangeable.

A helpful way is to group it like this:

• Ben = subject
• gözlüğümü = what was put
• defterin üstüne = where it was put
• koydum = action

So the structure is:

• I + my glasses + onto the notebook + put

That may feel backward from English, but it is very normal in Turkish. If you get used to saving the verb until the end, sentences like this become much easier to understand.