Cumartesi akşamı teyzemle tiyatroya gideceğim.

Cumartesi akşamı is a very common Turkish time expression meaning on Saturday evening / Saturday night.

In Turkish, combinations like day + part of the day often use a possessive ending on the second word:

• Pazartesi sabahı = Monday morning
• Cuma gecesi = Friday night
• Cumartesi akşamı = Saturday evening

So even though it may look strange from an English perspective, this is the normal pattern.
You may hear shortened forms in casual speech, but Cumartesi akşamı is the standard, natural version.

In Cumartesi akşamı, the -ı is a third-person possessive suffix, but in this kind of time expression it does not literally mean his/her/its evening in the way an English learner might expect.

It is part of a fixed grammatical pattern used to link time words:

• Cumartesi akşamı
• Pazar sabahı
• Yıl sonu
• Yaz tatili

So here, the suffix helps form a natural compound-like expression. It is best to learn Cumartesi akşamı as a whole time phrase.

Teyzemle breaks down like this:

• teyze = aunt
• -m = my
• -le = with

So:

• teyzemle = with my aunt

The suffix -le / -la means with and is attached directly to the noun.

Compare:

• arkadaşımla = with my friend
• annemle = with my mother
• otobüsle = by bus / with the bus

Yes. Teyzemle and teyzem ile both mean with my aunt.

• teyzemle = contracted, more common in everyday speech
• teyzem ile = slightly more separate/formal in feel

This works with many nouns:

• arkadaşımla = arkadaşım ile
• annemle = annem ile

In normal conversation, the attached form is usually preferred.

Because the verb gitmek means to go, and Turkish usually marks the destination with the dative case, which often corresponds to English to.

So:

• tiyatro = theater
• tiyatroya = to the theater

The ending here is -a / -e, but because the word ends in a vowel, Turkish inserts a buffer consonant y:

• okula = to school
• eve = to home / home
• sinemaya = to the cinema
• tiyatroya = to the theater

It is made of two parts:

• -a = dative ending (to)
• y = buffer consonant

Since tiyatro ends in a vowel, Turkish cannot attach another vowel directly without a connector, so it uses y:

• tiyatro + a → tiyatroya

This happens very often:

• araba + a → arabaya
• masa + a → masaya

Gideceğim means I will go and can be broken down as:

• git- = go
• -ecek / -acak = future tense
• -im / -ım / -um / -üm = I

But there is also a sound change:

• underlying stem: git-
• before the future suffix, it becomes gid-
• so: gid-ecek-im → gideceğim

So gideceğim = I will go

Related forms:

• gideceksin = you will go
• gidecek = he/she/it will go
• gideceğiz = we will go

This is a regular sound change in Turkish. Some verb stems ending in t become d when a vowel-initial suffix is added.

So:

• dictionary form: gitmek
• future form: gidecek
• not gitecek

You also see similar changes in some other words and forms. For learners, the best approach is simply to memorize that:

• gitmek → gidiyor, gidecek, gidin, etc.

Because of vowel harmony.

The future suffix has two forms:

• -ecek
• -acak

Which one you use depends on the vowel pattern of the verb stem. With git-, the correct form is -ecek:

• gitmek → gidecek
• gelmek → gelecek
• bakmak → bakacak
• olmak → olacak

So gideceğim follows normal vowel harmony.

In Turkish, the subject pronoun is often omitted because the verb ending already shows the person.

• gideceğim already means I will go
• so ben is unnecessary unless you want emphasis or contrast

Compare:

• Gideceğim. = I will go.
• Ben gideceğim. = I will go. / I’m the one who will go.

This is very common in Turkish.

Turkish word order is flexible, although the neutral order usually puts the verb at the end.

The original sentence:

• Cumartesi akşamı teyzemle tiyatroya gideceğim.

is very natural and neutral.

But you could also say:

• Teyzemle cumartesi akşamı tiyatroya gideceğim.
• Cumartesi akşamı tiyatroya teyzemle gideceğim.

These alternatives may shift the emphasis slightly, but the verb usually stays at the end in standard Turkish.

Strictly speaking, teyze traditionally means mother’s sister.

Turkish also has:

• hala = father’s sister
• amca = father’s brother
• dayı = mother’s brother

However, in everyday speech, teyze can also be used more broadly for an older woman in a polite or familiar way, depending on context.

So in this sentence, teyzem most naturally means my aunt in the family sense, especially my mother’s sister.

Turkish does not use articles the same way English does.

There is no direct equivalent of the in ordinary noun phrases, and a/an is only sometimes expressed with bir when needed.

So:

• tiyatroya can mean to the theater or to a theater, depending on context
• teyzemle means with my aunt
• Cumartesi akşamı means on Saturday evening

Turkish often leaves these details to context rather than marking them the way English does.