Learn Hardcore Turkish: Anons sistemi istasyonda çalışıyor. - The announcement system is working at the station.

Turkish has no articles such as a or the. Definiteness is shown by context, word order, and sometimes by case or possessive suffixes. In anons sistemi, for example, the suffix -i on sistem (see next question) also makes it definite (like the system).

Why does sistem appear as sistemi with -i? Isn’t that the accusative?

Here -i is the 3rd-person-singular possessive suffix, not the accusative. We’re looking at a noun–noun compound announcement system. In Turkish compounds, the head noun often takes a possessive ending (sistemi) while the modifier stays bare (anons).

How can I tell whether -i marks possession or the accusative case?

You decide by function:
• If it marks a definite object of a verb with an explicit subject, it’s accusative.
• If it belongs to a compound or indicates 3rd-person possession (like x’s system), it’s possessive.
In anons sistemi istasyonda çalışıyor, the phrase is a single compound noun, so -i is possessive.

Why does istasyon take -da to become istasyonda?

-da/-de is the locative case suffix, meaning at, in or on.
• Vowel harmony: after the back vowel o, you pick -da.
• Consonant assimilation: istasyon ends in n, so the suffix merges into -nda.
Result: istasyonda = at the station.

How is çalışıyor formed, and what does it mean?

çalışıyor = çalış- (verb root “work/operate”) + -ıyor (present continuous suffix)
There’s no extra word for is in Turkish; çalışıyor itself means is working or is functioning right now. For habitual simple present you’d use çalışır, and for past çalıştı.

Why isn’t there a separate verb for to be in is working like in English?

In Turkish, action verbs like çalışmak already express the activity and the state of being at once. You don’t add a separate copula. Even with nouns or adjectives in the present, the copula is usually omitted:
O doktor = He’s a doctor (not doktor-dur in spoken Turkish).

Could I say istasyona instead of istasyonda if I meant to the station?

Yes, but that changes the meaning:
• istasyonda (locative) = at the station
• istasyona (dative) = to/towards the station
Since çalışmak here means to function/work, you state where it works (at the station), not where to.

How do I turn this into a question or make it negative?

• Question: add the particle mu/mi/mu/mü after the verb as a separate word:
Anons sistemi istasyonda çalışıyor mu?
• Negative: insert -m- before -ıyor:
Anons sistemi istasyonda çalışmıyor.