Learn Hardcore Turkish: Çarşamba akşamı parkta çay içeceğim. - On Wednesday evening, I will drink tea in the park.

It’s not accusative here. Akşamı is the 3rd‑person possessive form in a fixed time expression meaning “the evening of [X].” In time phrases, Turkish often drops the possessor’s genitive:

Full form (more formal): Çarşamba’nın akşamı
Common/neutral: Çarşamba akşamı (“Wednesday evening”) Similar patterns: Pazartesi sabahı (Monday morning), Cumartesi gecesi (Saturday night). So the -ı in akşamı is “its evening,” not the object marker.

Why is it parkta, not parkda?

The locative suffix is underlyingly -DA/-DE, but after a voiceless consonant (p, ç, t, k, f, h, s, ş) it surfaces as -TA/-TE. Since park ends in voiceless k, you get parkta. Vowel harmony chooses -ta (back vowel a) instead of -te. Compare:

okulda (at school), evde (at home)
kitapta (in the book), köprüde (on the bridge)

Why isn’t çay marked like çayı?

Indefinite direct objects in Turkish are unmarked (no accusative). Çay içeceğim = “I’ll drink tea (some tea).” If you say çayı içeceğim, you mean a specific/known tea: “I’ll drink the tea.”

How is içeceğim formed, and why the letter ğ?

Verb root: iç- (drink)
Future: -(y)ecek (front-vowel form because of i in iç-)
1st singular: -im When a vowel-initial ending follows, the k of -ecek typically softens to ğ: iç-ecek-im → iç-eceğ-im = içeceğim. The same happens in plural: içeceğiz. Other examples: yapacağım, bakacağım.

How do you pronounce içeceğim, especially ğ?

Turkish ğ doesn’t make a hard “g” sound; it lengthens/smooths the preceding vowel and can create a slight glide. içeceğim is roughly “ee-cheh-JEEM,” with a lengthened “e” before ğ: [itʃeˈdʒeːjim]. Don’t pronounce ğ as a hard consonant.

Where is the subject “I”? Do I need to say ben?

The verb ending already shows the subject. İçeceğim = “I will drink.” You add ben only for emphasis/contrast: Ben içeceğim (I will, not someone else).

What’s the usual word order? Can I move things around for emphasis?

Neutral order is typically time → place → object → verb: Çarşamba akşamı parkta çay içeceğim. The item immediately before the verb is in focus. So this sentence naturally focuses çay (tea). To emphasize the place, move it right before the verb, e.g., Çarşamba akşamı çayı parkta içeceğim (and note the definite çayı if you mean “the tea”).

Does Çarşamba akşamı mean “this Wednesday evening,” “next,” or something else?

On its own it usually refers to the relevant/coming Wednesday from context. To be explicit:

This Wednesday evening: bu Çarşamba akşamı
Last Wednesday evening: geçen Çarşamba akşamı
Next Wednesday evening: gelecek or önümüzdeki Çarşamba akşamı
Every Wednesday evening: Çarşamba akşamları or her Çarşamba akşamı

Can I say Çarşamba akşamında to mean “on Wednesday evening”?

That’s not the idiomatic way. Use Çarşamba akşamı. For a general “in the evening,” you can say akşamleyin; for “Wednesday night,” use Çarşamba gecesi.

Does parkta mean “in the park” or “at the park”? What if I mean “to the park”?

-DA/-DE (here -ta) covers both “in” and “at,” so parkta can mean either depending on context. For motion toward, use dative -A/-E: parka (“to the park”). To emphasize being inside, say parkın içinde (“inside the park”).

How do I make it a question or negate it?

Negative: içmeyeceğim (iç- + -me negation + -yecek future + -im 1sg).
Yes/no question: add the separate question particle mi/ mı/ mu/ mü after the verb; the person ending goes on the particle:
• 1sg: içecek miyim?
• 2sg: içecek misin?
• 3sg: içecek mi?
Example: Çarşamba akşamı parkta çay içecek misin?

How do I say “a tea” or “one tea”? Is çay countable?

Use bir çay for “a/one tea” (as in one glass/cup). You can count: iki çay, üç çay. Without bir, çay içeceğim just means “I’ll drink tea” (unspecified amount).

What’s the difference between akşam and gece? What if I mean “Wednesday night”?

Akşam = evening (roughly until night), gece = night. “Wednesday night” is Çarşamba gecesi. Your sentence with akşamı specifically targets the evening.

Any spelling/capitalization tips for this sentence?

Days of the week are capitalized: Çarşamba.
akşamı, parkta, çay are lower-case.
Keep Turkish diacritics: Ç, ş, ı, ğ. Note the dotless ı in akşamı and the soft ğ in içeceğim.