Silindir kilit kamera gözetimi altında değiştirildi.

It is a stacked verb form:

• değiş- = change
• değiştir- = change something, alter, replace
• -il- = passive
• -di = past tense

So değiştirildi means was changed or, in many practical contexts like locks, was replaced.

That is why the whole sentence sounds like The cylinder lock was changed/replaced under camera surveillance.

Because the sentence describes something that was done to the lock by someone.

• değişti = it changed / it became different
• değiştirildi = it was changed / someone changed it

With a lock, Turkish usually uses değiştirmek when a person replaces or swaps it out. So değiştirildi is the natural choice here.

The grammatical subject is Silindir kilit.

Even though, in real life, a person did the action, the sentence is in the passive, so the thing affected by the action becomes the focus:

• Silindir kilit ... değiştirildi. = The cylinder lock was changed.

The person or people who changed it are not mentioned.

Turkish often leaves the agent unstated in passive sentences, just like English does.

So:

• Silindir kilit kamera gözetimi altında değiştirildi. = The cylinder lock was changed under camera surveillance.

If you really wanted to mention who did it, Turkish could add tarafından:

• Silindir kilit görevli tarafından değiştirildi. = The cylinder lock was changed by the attendant/staff member.

But in normal usage, leaving the doer out is very common.

It means under camera surveillance, under camera monitoring, or while being monitored by camera.

Breakdown:

• kamera = camera
• gözetim = surveillance, monitoring, supervision
• gözetimi = camera surveillance as a noun compound
• altında = under

So the whole phrase literally feels like under the surveillance of camera monitoring, but the natural English meaning is simply under camera surveillance.

Because kamera gözetimi is a very common Turkish noun-compound pattern.

In this pattern:

• the first noun modifies the second noun
• the second noun usually takes a 3rd person possessive ending

So:

• kamera gözetimi = camera surveillance
• polis gözetimi = police surveillance
• doktor kontrolü = doctor’s examination/checkup

That -i in gözetimi is part of the compound structure. It does not mean it by itself here.

Because Turkish, like English, uses under in some abstract expressions.

Compare English:

• under pressure
• under control
• under observation

Turkish does the same:

• baskı altında = under pressure
• kontrol altında = under control
• gözetim altında = under surveillance

So kamera gözetimi altında is a normal idiomatic expression.

Because Turkish has no articles like English a/an/the.

So Silindir kilit can mean:

• the cylinder lock
• a cylinder lock

The exact meaning depends on context.

In many real situations, English will choose the because the speaker has a specific lock in mind, but Turkish does not need a separate article to show that.

Yes, that is the general idea.

silindir is modifying kilit, so together they mean a type of lock: cylinder lock.

In technical or hardware contexts, the most natural English equivalent may vary a little depending on the exact object:

• cylinder lock
• cylindrical lock
• sometimes even lock cylinder in certain contexts

For a learner, the key point is that silindir kilit is a unit meaning a specific kind of lock, not two separate unrelated nouns.

Yes, the word order can be changed for emphasis, but the given order is very natural.

Turkish usually places the verb at the end, and adverbial phrases often come before it:

• Silindir kilit kamera gözetimi altında değiştirildi.

You could also say:

• Kamera gözetimi altında silindir kilit değiştirildi.

That puts more focus on under camera surveillance.

So the sentence is flexible, but keeping değiştirildi at the end is the most typical pattern.

A natural active version would be:

• Birisi silindir kilidi kamera gözetimi altında değiştirdi. = Someone changed the cylinder lock under camera surveillance.

Notice the difference:

• passive: silindir kilit ... değiştirildi
• active: birisi silindir kilidi ... değiştirdi

In the active sentence, the lock is the direct object, so it appears in the object form kilidi. In the passive sentence, the focus shifts to the lock itself, so that object marking is no longer there.

Technically it means was changed, but in real-world contexts like locks, parts, batteries, passwords, and so on, Turkish değiştirmek often corresponds to English replace.

So here, native English speakers will often understand it best as:

• The cylinder lock was replaced under camera surveillance.

Both changed and replaced are possible, but replaced is often the more natural English choice in this kind of sentence.