Yangın büyüyünce itfaiyeyi çağırmak zorunda kaldık.

Büyüyünce comes from the verb büyümek (to grow, become bigger).

It breaks down like this:

• büyü- = verb stem
• -(y)ınca / -(y)ince / -(y)unca / -(y)ünce = a suffix meaning when, once, or after

So büyüyünce means when it grew / when it got bigger.

In this sentence, Yangın büyüyünce means when the fire got bigger or once the fire grew.

That y is a buffer consonant.

In Turkish, when a word stem ends in a vowel and the next suffix begins with a vowel, a buffer consonant is often inserted to make pronunciation easier.

Here:

• büyü- ends in a vowel
• the -ince type suffix begins with a vowel

So Turkish inserts y:

• büyü + ünce would be awkward
• büyü-y-ünce becomes büyüyünce

This is very common in Turkish.

This is because of vowel harmony.

The suffix is basically -(y)IncA, and its vowels change to match the vowels in the stem.

Since büyü- contains the vowel ü, the suffix becomes -yünce.

So:

• gelmek → gelince
• bakmak → bakınca
• okumak → okuyunca
• büyümek → büyüyünce

A learner does not need to memorize each form separately; it is the same suffix behaving according to Turkish vowel harmony.

The ending -yi is the definite accusative marker.

In Turkish, a direct object often takes the accusative ending when it is specific/definite. Here, itfaiyeyi means the fire department / the fire brigade as a specific thing being called.

Breakdown:

• itfaiye = fire department / fire brigade
• -yi = accusative ending

The y is again a buffer consonant, because itfaiye ends in a vowel.

So:

• itfaiye + i → itfaiyeyi

Because Turkish uses the infinitive -mak / -mek form before expressions like zorunda kalmak.

So the structure is:

• çağırmak = to call
• zorunda kalmak = to have to, to be forced/obliged to

Together:

• çağırmak zorunda kaldık = we had to call

This is very normal Turkish grammar. After zorunda kalmak, the main action is usually in the infinitive.

Zorunda kaldık means we had to or we were forced to.

More literally:

• zorunda = under obligation / obliged
• kaldık = we remained / we ended up

But in natural English, you should understand zorunda kalmak as a set expression meaning to have to.

So:

• gitmek zorunda kaldım = I had to go
• beklemek zorunda kaldılar = they had to wait
• çağırmak zorunda kaldık = we had to call

Yes, by itself kalmak often means to stay or to remain.

But in the expression zorunda kalmak, it has a more idiomatic meaning: to end up having to or to be left with no choice but to.

So in this sentence, kaldık does not mean we stayed. It is part of the fixed pattern:

• V-mak zorunda kalmak = to have to do V

This pattern often carries a slight sense of necessity caused by circumstances.

Turkish often leaves out subject pronouns because the verb ending already shows the subject.

Here, kaldık tells you the subject is we:

• -dık / -dik / -duk / -dük = past tense
• -k = we

So kaldık means we remained / we had to.

Because the verb already shows we, adding biz is optional:

• Yangın büyüyünce itfaiyeyi çağırmak zorunda kaldık.
• Biz yangın büyüyünce itfaiyeyi çağırmak zorunda kaldık.

Both are possible, but the version without biz is very natural.

Because Turkish is typically a verb-final language.

The main conjugated verb usually comes at the end, and everything else appears before it.

So the sentence is arranged like this:

• Yangın büyüyünce = when the fire got bigger
• itfaiyeyi çağırmak = to call the fire department
• zorunda kaldık = we had to

This kind of structure is very normal in Turkish. English speakers often need time to get used to waiting until the end for the main verb.

Turkish does not have articles like English the and a/an in the same way.

So yangın can mean:

• fire
• the fire

The exact meaning depends on context.

In this sentence, English naturally says the fire because it is a specific fire being talked about. Turkish does not need a separate word for the.

Yes, in many contexts they can be similar, but they are not always identical in tone.

• büyüyünce often means when / once / after it grew
• büyüdüğünde also means when it grew / when it was bigger, but can sound a little more neutral or descriptive depending on context

In everyday Turkish, -ince forms are very common for events that lead to the next action:

• Yangın büyüyünce itfaiyeyi çağırmak zorunda kaldık.

This feels very natural: when the fire got bigger, we had to call the fire department.

Yes. Turkish commonly uses büyümek not only for living things or children, but also for situations, problems, and fires becoming larger or more serious.

So a fire can büyümek:

• Yangın büyüdü. = The fire got bigger.
• Sorun büyüdü. = The problem grew / got worse.

So this usage is completely natural.