Learn Hardcore Turkish: Bugün tiyatroya gideceğim, tiyatro bileti çoktan alındı. - I will go to the theater today; the theater ticket has already been bought.

tiyatro = theatre
dative ending -a attaches, but since tiyatro ends in a vowel, Turkish inserts a buffer consonant y:
- tiyatro + a → tiyatroya = to the theatre

More examples with the same pattern:

okul + a → okula (to the school)
havaalanı + a → havaalanına (to the airport)
araba + a → arabaya (to the car)

Why is there no ben (I) before gideceğim?

In Turkish, the personal ending on the verb already shows the subject, so the pronoun is usually omitted unless you want to emphasize it.

gideceğim = gid (go) + ecek (future) + -im (I)
→ I will go

So:

Bugün tiyatroya gideceğim. = Today I will go to the theatre.
You only add ben for emphasis or contrast:
Bugün ben tiyatroya gideceğim (o değil).
Today I will go to the theatre (not him/her).

What exactly does gideceğim mean, and how is it formed?

Gideceğim is the future tense, 1st person singular of gitmek (to go).

Formation:

stem: git-
future suffix: -ecek / -acak → here -ecek
1st person singular ending: -im

Phonetic changes:

git + ecek → the t often becomes d before a voiced sound: gidecek
gidecek + im → gideceğim (vowel harmony and normal speech contraction)

Meaning: I will go / I am going to go (future).

Why is tiyatro bileti used, not just bilet?

Tiyatro bileti is a noun–noun compound, literally theatre ticket, telling you what kind of ticket it is.

tiyatro = theatre
bilet = ticket
bilet + i in this pattern is the standard compound form, similar to of-phrases in English:
- okul kapısı = school door (the door of the school)
- ev telefonu = home phone

So tiyatro bileti means theatre ticket as a unit.
The -i here is not the object (accusative) ending; it’s the second part of a compound noun.

Is tiyatro bileti the subject or the object of alındı?

In this sentence, tiyatro bileti is the subject.

Active: Birisi tiyatro biletini aldı.
Someone bought the theatre ticket.
- biletini = object (accusative)
Passive: Tiyatro bileti alındı.
The theatre ticket was bought.
- tiyatro bileti becomes the subject of the passive verb.

So in tiyatro bileti çoktan alındı, the ticket is what "was bought" → it’s the subject of the passive verb.

Why is alındı used instead of aldım? What’s the difference?

aldım = I bought (it) → active, subject I
alındı = was bought → passive, no explicit subject

Using alındı de-emphasizes who bought the ticket and emphasizes the result: the ticket is already bought.

Compare:

Tiyatro biletini çoktan aldım.
I already bought the theatre ticket. (focus on me doing it)
Tiyatro bileti çoktan alındı.
The theatre ticket has already been bought. (focus on the state/result)

Why is the English translation often “has already been bought” when alındı looks like simple past?

Turkish -dı past can cover both:

simple past: was bought
present perfect: has been bought

Context words like çoktan (already, long ago) help.
So alındı with çoktan naturally matches “has already been bought” in English, even though morphologically it’s just past tense passive:

alın- (be taken/bought) + -dı (past) → alındı
Meaning in context: the buying is completed before now → has already been bought.

What does çoktan add, and where does it usually go in the sentence?

Çoktan means roughly already / long since / by now. It emphasizes that the action was done earlier than expected, and is fully completed.

In tiyatro bileti çoktan alındı:

plain: Tiyatro bileti alındı. → The ticket was bought.
with çoktan: Tiyatro bileti çoktan alındı. → The ticket has already been bought (a while ago / in good time).

Position: it normally comes before the verb or in the adverb cluster:

Bilet çoktan alındı.
Bilet çoktan alınmış.

Putting it elsewhere (e.g. çoktan bilet alındı) is possible but much less natural in neutral word order.

Could I use zaten instead of çoktan? What’s the difference?

Both can be translated as already, but they’re not identical:

çoktan → focuses on time: already, long ago, by now
- suggests it was done well in advance or earlier than you might think
zaten → focuses on obviousness / expectation: already, anyway, as you know
- suggests this is not surprising information

Examples:

Tiyatro bileti çoktan alındı.
The theatre ticket has already been bought (some time ago).
Tiyatro bileti zaten alındı.
The theatre ticket is already bought anyway (as we said / as you know).

In your sentence, çoktan sounds more like in good time / earlier.

Can I change the word order and say Bugün gideceğim tiyatroya?

That order is technically possible but sounds unnatural in neutral speech. The normal order is:

Bugün tiyatroya gideceğim.

Turkish prefers:

Adverb (time/place)
- complements
  - verb
    → Today + to the theatre + will go

You can move words for emphasis:

Tiyatroya bugün gideceğim. (emphasis on today, not another day)
Bugün ben tiyatroya gideceğim. (emphasis on I, not someone else)

But Bugün gideceğim tiyatroya would usually be used only in very marked, poetic, or contrastive contexts.

Why isn’t there an “it” subject like in English (it has been bought)?

Turkish doesn’t use dummy subjects like English it or there. The actual thing we’re talking about is the subject:

English: It has already been bought.
Turkish: Tiyatro bileti çoktan alındı.
(The theatre ticket has already been bought.)

No extra “it” is needed; tiyatro bileti itself is the subject of alındı.