Can yeleğini giymek üzereyken deniz tutması başladı.

Here, Can is a male first name.

A native English speaker might expect can to be the English modal verb, but in Turkish Can is a common name.

A useful pronunciation note:

• Can in Turkish is pronounced roughly like John in English, not like English can.

So the sentence is talking about a person named Can.

Yeleğini comes from yelek, which means vest, waistcoat, or in some contexts life jacket depending on the situation.

It breaks down like this:

• yelek = vest
• yeleği = his/her vest
• yeleğini = his/her vest as a definite direct object

So in this sentence, yeleğini giymek means:

• to put on his vest
• or, depending on context, to put on his life jacket

Because Turkish is marking two things at once:

1. Possession

   • yeleği = his/her vest

2. Definite direct object

   • yeleğini = his/her vest as the thing being put on

So:

• yelek = vest
• yeleği = his/her vest
• yeleğini = his/her vest (the object of the verb)

This is very common in Turkish. When a possessed noun is also the direct object, it usually takes this extra accusative marking.

giymek üzereyken means something like:

• when he was about to put on
• just as he was about to put on
• while he was on the point of putting on

Breakdown:

• giymek = to wear / to put on
• üzere = about to, on the point of
• -yken = while / when

So giymek üzereyken expresses an action that was just about to happen, but had not happened yet.

This is stronger and more specific than simply saying giyerken:

• giyerken = while putting on / while wearing
• giymek üzereyken = just when he was about to put on

-yken means while or when.

It attaches to a word or phrase and turns it into a kind of time clause.

So:

• üzereyken = while being about to, or more naturally, when about to

In the full sentence:

• Can yeleğini giymek üzereyken = When Can was about to put on his vest...

Then the main clause follows:

• deniz tutması başladı = seasickness began

Because the meaning is different.

• giyerken = while putting on / while wearing
• giymek üzereyken = just as he was about to put on

So giymek üzereyken tells you the action had not happened yet. He was at the point of doing it.

That nuance matters in this sentence: the seasickness started before or just as he was going to put the vest on.

deniz tutması is an idiomatic Turkish expression meaning seasickness.

Literally, it comes from:

• deniz = sea
• tutmak = to hold, catch, seize
• tutması = its catching / the act of catching

So the expression suggests something like:

• being caught by the sea
• the sea taking hold of someone

In natural English, that becomes seasickness.

Turkish often uses tutmak in expressions for conditions that suddenly affect someone.

Because tutması is a verbal noun form built from tutmak.

Very roughly:

• tutma = catching / holding
• tutması = its catching / the catching

In expressions like deniz tutması, araba tutması, and similar patterns, this structure becomes a fixed way to name a condition.

So you do not need to translate the grammar word-for-word every time. It is best learned as a set expression:

• deniz tutması = seasickness

başladı means started or began.

The subject is:

• deniz tutması = seasickness

So:

• deniz tutması başladı = seasickness started

Literally, Turkish says that the seasickness began. English might also say:

• He started to feel seasick
• Seasickness hit him

But the Turkish sentence is structured around seasickness as the subject.

Because Turkish often leaves pronouns out when they are understood from context.

Here, the sentence starts with Can, so we already know who the person is. There is no need to add a separate he.

Also, in the first part:

• Can yeleğini giymek üzereyken
  it is understood that Can is the one who is about to put on the vest.

Turkish frequently relies on context and structure instead of repeating pronouns.

The sentence is structured like this:

• Can yeleğini giymek üzereyken = When Can was about to put on his vest
• deniz tutması başladı = seasickness started

So the pattern is:

time clause + main clause

A more literal word-for-word order would be:

• Can his-vest put-on about-to-when seasickness started

This may feel backwards compared with English, but it is very normal in Turkish to place the background or time information first.

It is close, but not exact.

That English version suggests he was already in the middle of putting it on.

The Turkish giymek üzereyken is more precise:

• when he was just about to put it on
• just as he was about to put it on

So a better translation would be:

• Just as Can was about to put on his vest, seasickness started.

Or more natural English:

• Just as Can was about to put on his vest, he started to feel seasick.

By itself, yelek usually means vest or waistcoat.

But in context, it can sometimes refer to a more specific kind of vest, such as:

• life jacket
• protective vest

If the broader context is about a boat or the sea, many learners would naturally wonder whether yeleğini means his life jacket. That is possible depending on the situation, even though the word itself is simply vest unless further specified.

The main verb başladı is in the simple past tense:

• başladı = started / began

The phrase giymek üzereyken is not a simple tense form by itself. It is a time expression meaning:

• when he was about to wear/put on

So the whole sentence describes a past event:

• Can was about to do something,
• and at that moment, seasickness began.