Learn Hardcore Turkish: Öğrenciler işbirliği ile karmaşık projeleri kolayca tamamlıyor. - The students easily complete complex projects through cooperation.

İle is a postposition meaning with or by means of. It always follows a noun in the nominative case, so işbirliği remains in its base form. This construction literally translates to with cooperation.

Why does the verb tamamlıyor not include a plural marker like -lar when the subject öğrenciler is plural?

In the present continuous tense, the suffix -yor combines with the stem to form tamamlıyor, which by default covers both 3rd person singular and plural if the subject is explicitly stated. Because öğrenciler is marked for plural by -ler, you don’t need an extra -lar on the verb. Adding that suffix (tamamlıyorlar) is grammatically correct but often omitted for brevity.

Can işbirliği ile be replaced by işbirliğiyle? What is the stylistic difference?

Yes. Affixing -yle (after a vowel) produces işbirliğiyle, which also means with cooperation. Using ile as a separate word tends to sound more formal or emphatic, while -yle is more colloquial. A buffer consonant y appears between i and -yle to ease pronunciation.

Why does karmaşık projeleri take the accusative suffix -i, and what does that indicate?

Turkish marks definite direct objects with the accusative suffix -i/-ı/-u/-ü. Since karmaşık projeleri refers to specific, known projects, it receives -i. If the phrase were indefinite (some complex projects), you would say karmaşık projeler without the suffix.

How is the adverb kolayca derived from the adjective kolay, and why is this derivation necessary?

To turn the adjective kolay (easy) into an adverb (easily), you add -ca/-ce, resulting in kolayca. Turkish adjectives cannot directly modify verbs, so the adverbial suffix is necessary.

What tense or aspect does tamamlıyor express, and is there a simple present equivalent?

Tamamlıyor is the present continuous (progressive) tense, marked by -iyor. Turkish lacks a simple present like English; instead, the aorist suffix -r (as in tamamlar) can indicate habitual actions. Here, tamamlıyor suggests an ongoing or repeated action.

Could birlikte replace işbirliği ile, and how would that affect nuance?

Yes. Birlikte means together. You could say Öğrenciler birlikte karmaşık projeleri kolayca tamamlıyor. This version emphasizes that students are acting simultaneously, while işbirliği ile highlights the structured or cooperative method.