Onun adı aklıma gelmiyor.

Because onun is the genitive form of o and means his/her/its.

• o = he / she / it / that
• onun = his / her / its / that one’s

In Turkish, possession is often shown in two places:

• the possessor gets the genitive ending: onun
• the possessed noun gets a possessive ending: adı

So:

• onun adı = his/her name

Using o adı would not be correct here.

Ad means name.

Here, it becomes adı because it has the 3rd person possessive suffix, meaning his/her/its name.

So:

• ad = name
• adı = his/her/its name

This is part of the common Turkish possession pattern:

• benim adım = my name
• senin adın = your name
• onun adı = his/her name

So in this sentence, adı already includes the idea of his/her.

Good question. In many cases, onun can actually be omitted if the meaning is clear from context.

• Adı aklıma gelmiyor. = His/her name isn’t coming to mind.
• Onun adı aklıma gelmiyor. = His/her name isn’t coming to mind.

Adding onun makes it more explicit or contrastive. It can help if you want to emphasize that person’s name specifically.

So:

• adı alone can be enough
• onun adı is more explicit

Aklıma comes from akıl, which means mind.

It breaks down like this:

• akıl = mind
• aklım = my mind
• aklıma = to my mind

So the sentence literally has the idea:

• his/her name is not coming to my mind

This is a very natural Turkish way to express remembering or failing to remember something.

This happens because of a common sound change in Turkish.

The word akıl loses its second vowel when certain suffixes are added:

• akıl
• aklım
• aklıma

This type of vowel drop happens in a number of Turkish words.

So although the dictionary form is akıl, when suffixes are attached it often becomes akl-.

That -a is the dative case ending, which often means to or toward.

So:

• aklım = my mind
• aklıma = to my mind

The expression aklına gelmek literally means to come to someone’s mind.

Examples:

• Aklıma geldi. = It came to my mind. / I remembered it.
• Aklıma gelmiyor. = It’s not coming to my mind. / I can’t remember.

Yes, very much so.

Literally, it means to come to my mind, but in natural English it often corresponds to things like:

• to remember
• to come to mind
• to occur to me

So Onun adı aklıma gelmiyor is a very natural Turkish way to say that you can’t remember someone’s name.

This is a common pattern in Turkish:

• Aklıma bir fikir geldi. = An idea came to mind.
• Onu bir türlü aklıma getiremiyorum. = I just can’t bring it to mind.

Gelmiyor breaks down like this:

• gel- = come
• -mi- = negation
• -yor = present continuous / current ongoing situation

So:

• geliyor = is coming
• gelmiyor = is not coming

In this sentence, gelmiyor does not necessarily mean something is physically moving right now. Turkish often uses -yor for a present situation that is currently true.

So here it means something like:

• isn’t coming to mind
• I can’t remember

Because the grammatical subject in Turkish is not I here.

The subject is onun adı = his/her name.

So literally the structure is:

• His/her name
  • to my mind
    • is not coming

That is why the verb is third person singular:

• gelmiyor = it is not coming

Even though the natural English meaning is I can’t remember his/her name, Turkish expresses it from the perspective of the name not coming to mind.

Turkish word order is often different from English, and verbs usually come at the end.

This sentence is:

• Onun adı = his/her name
• aklıma = to my mind
• gelmiyor = isn’t coming

So the literal order is:

• His/her name to my mind isn’t coming.

That may sound unusual in English, but it is completely normal in Turkish.

Also, Turkish relies heavily on suffixes, so the role of each word is often clear even when the order differs from English.

Yes. Turkish has both ad and isim for name.

So you may also hear:

• Onun ismi aklıma gelmiyor.

This is also natural and understandable.

Very roughly:

• isim is extremely common in everyday speech
• ad can sound a bit more native/Turkic or sometimes slightly more formal depending on context

But in this sentence, both work.

Yes.

Turkish does not mark grammatical gender in pronouns like English does. So:

• onun can mean his, her, or its

Therefore:

• Onun adı aklıma gelmiyor. can mean I can’t remember his name or I can’t remember her name

The context tells you which one is meant.

Yes, but the nuance is a little different.

• Onun adını hatırlamıyorum. = I don’t remember his/her name.
• Onun adı aklıma gelmiyor. = His/her name isn’t coming to mind.

Both can work in similar situations, but aklıma gelmiyor often suggests that you are trying to recall it and it just won’t come to you at that moment.

So it can feel a bit more like:

• It’s on the tip of my tongue
• I’m blanking on the name

Because adı is the subject of the sentence, not the direct object.

In Onun adı aklıma gelmiyor:

• onun adı = the thing that is not coming
• aklıma = to my mind
• gelmiyor = isn’t coming

If you used a verb like hatırlamak, then his/her name would be the object, and you would use the accusative:

• Onun adını hatırlamıyorum.

So compare:

• adı aklıma gelmiyor = his/her name isn’t coming to mind
• adını hatırlamıyorum = I don’t remember his/her name

Yes, very common.

Turkish often expresses remembering with aklına gelmek. You will hear similar sentences such as:

• Şu an adı aklıma gelmiyor. = I can’t remember the name right now.
• Neydi, aklıma gelmedi. = What was it? I couldn’t remember.
• Birden aklıma geldi. = It suddenly came to mind.

So this sentence is not unusual or literary; it is a normal everyday way to speak.