Learn Hardcore Turkish: Tesadüf bu ya, bugün parkta seninle yine karşılaştım. - What a coincidence, I ran into you again in the park today.

It’s an idiomatic, conversational opener meaning roughly “as luck would have it” or “what a coincidence.” You put it at the start of a sentence to frame an unexpected or ironic coincidence. It’s informal and adds a storytelling tone.

What is ya doing here? Is it the same as the ya … ya … construction?

Here ya is a discourse particle that adds emphasis/attitude (surprise, mild drama). It isn’t the ya … ya … pattern meaning “either … or ….” You can’t translate it literally; think of it like a conversational “you know” or “man” added for flavor.

Why is it seninle and not seni after karşılaştım?

Because karşılaşmak (“to run into, meet by chance”) doesn’t take a direct object; it uses the comitative ile (“with”): biriyle karşılaşmak = “to run into someone.” Using seni (accusative) would be ungrammatical here.

Can I say senle instead of seninle?

Yes. Seninle is the standard form; senle is common and more colloquial. Similarly: benimle/benle, onunla/onla (the shorter forms are informal).

What’s the difference between karşılaşmak and karşılamak? I get them mixed up.

Karşılaşmak: to run into/meet (by chance), uses -ile: Ali’yle karşılaştım.
Karşılamak: to meet/welcome (on purpose) or to cover (a cost), takes accusative: Ali’yi karşıladım (“I went to meet/welcome Ali”).

How is karşılaştım built, and why is it a t and not a d in the past tense?

karşı (opposite/facing) + -laş- (become/do mutually) → “come face to face, meet”
- past tense -di → becomes -tı after voiceless ş (consonant harmony)
- 1st person sg -m Result: karşı-laş-tı-m = “I ran into (someone).”

Why is it parkta and not parka?

-da/-de (locative) means “in/at/on”: parkta = “at/in the park.”
-a/-e (dative) means “to/toward”: parka = “to the park.”
Since the meeting happened in the park, the locative is correct.

What’s the nuance of yine here? Could I use tekrar, yeniden, or gene instead?

yine/gene: “again/once again.” Gene is more colloquial; both fit here.
tekrar: “again/anew” (also “repetition”); a bit more formal/explicit but fine: tekrar karşılaştım.
yeniden: “again, anew (after a break/start over).” Works for reunions after time (e.g., “years later we met again”), but for a casual repeat encounter like this, yine/gene is most natural.

Is the word order fixed? Can I move things around?

Turkish word order is flexible for emphasis. All of these are fine, with different focus:

Bugün parkta seninle yine karşılaştım. (neutral)
Bugün parkta yine seninle karşılaştım. (slight focus on “again”)
Parkta bugün seninle yine karşılaştım. (focus on “at the park today”) The verb typically stays at/near the end.

Why is there no ben? Do I need to say “Ben … karşılaştım”?

You don’t need it. The ending -m on karşılaştım already marks “I.” Adding Ben is only for emphasis or contrast: Ben bugün parkta… (“I, today at the park…”).

Should it be karşılaştık (“we ran into each other”) instead of karşılaştım?

Both are common:

Seninle karşılaştım: “I ran into you.” (speaker-centered)
Karşılaştık (optionally with seninle): “We ran into each other.” (mutual perspective) Pick based on which perspective you want.

Could I say Tesadüfen, bugün parkta seninle yine karşılaştım instead of Tesadüf bu ya?

Yes. Tesadüfen is the neutral adverb “by coincidence/accidentally.” Tesadüf bu ya is more idiomatic and expressive, adding a storyteller’s “as luck would have it” feel.

How is this different from Bugün parkta seni yine gördüm?

seni gördüm: “I saw you (again).” It’s just visual noticing.
seninle karşılaştım: “I ran into you (again).” It implies an encounter/meeting, not just seeing from afar.

Are there other verbs for “run into,” and what cases do they take?

Yes:

birine rastlamak (dative -e): Sana parkta rastladım.
birine denk gelmek (dative -e): Ayşe’ye denk geldim.
biriyle karşılaşmak (with -le/ile): Ali’yle karşılaştım. All mean “run into,” but karşılaşmak feels more like a mutual encounter.

Is the comma after Tesadüf bu ya necessary?

It’s standard to separate this introductory, idiomatic chunk with a comma: Tesadüf bu ya, … In informal texting you might see it omitted, but the comma is good practice.

Is seninle informal? How would I make this polite/formal?

Use the polite siz forms:

Sizinle yine karşılaştım. = “I ran into you (polite) again.” Everything else stays the same; the verb still shows the speaker is “I.”