Learn Hardcore Turkish: Arkadaşım sakal stilini değiştirdiğinde, onun başka biri olduğunu zannetmiştim. - When my friend changed his beard style, I thought he was someone else.

It means “when he changed” his beard style. In Turkish, attaching “-diğinde” to the verb forms a temporal subordinate clause. This clause sets the time frame—it tells us that the speaker’s mistaken assumption occurred at the moment his friend changed his beard style.

Why is “zannetmiştim” used instead of a simple past form like “zannedim”?

The verb “zannetmiştim” is in the pluperfect (past perfect) form, which implies that the speaker’s assumption was held in the past and that hindsight or a later realization has now invalidated it. The “-miş” component can also indicate a sense of hearsay or reported information, adding a layer of retrospective reflection about that mistaken belief.

How is possession expressed in “sakal stilini”?

In “sakal stilini,” the suffix “-ini” attached to “stil” (style) denotes possession, meaning “his beard style.” Turkish frequently incorporates possessive suffixes directly on nouns, so the beard style is understood to belong to the friend mentioned earlier in the sentence.

Why does the sentence begin with the subordinate clause and then use a comma?

In Turkish sentence structure, it is common to lead with subordinate clauses—for example, time clauses—and follow them with the main clause. The comma clearly separates the dependent clause “Arkadaşım sakal stilini değiştirdiğinde” (when my friend changed his beard style) from the main clause “onun başka biri olduğunu zannetmiştim” (I had thought he was someone else), providing clarity about the timing of the events.

What is the function of “onun” in the latter part of the sentence?

The pronoun “onun” refers back to the friend. In the clause “onun başka biri olduğunu zannetmiştim” it indicates that the speaker thought “he was someone else.” This pronoun is used to keep the reference clear, linking the friend’s changed appearance directly to the speaker’s altered perception.

What does the phrase “başka biri” imply in this context?

While “başka biri” literally translates to “another person,” in this context it suggests that the friend appeared completely different after changing his beard style. It emphasizes the speaker’s surprise or disbelief at how dramatically the friend’s appearance—and perhaps demeanor—had transformed, making him seem like an entirely different person.