Learn Hardcore Korean: osi gugyeojyeosseul ttae darimiro darimjilhaeyo. - When clothes are wrinkled, iron them with an iron.

구기다 means “to wrinkle” or “to crush.”
Its passive/intransitive form is 구겨지다, meaning “to get wrinkled.”
Adding the past tense marker -었- gives 구겨졌- (“has gotten wrinkled”).
Appending -을 때 (“when”) yields 구겨졌을 때, literally “when (it) has become wrinkled.”

So 옷이 구겨졌을 때 means “when the clothes are wrinkled” or “once the clothes have become wrinkled.”

What’s the difference between using -었을 때 and -으면 in this sentence?

-었을 때 focuses on the time after something has happened (“at the time when”).
-으면 is a conditional “if/when,” often implying “whenever” or “if it gets wrinkled.”

Both are possible here:
• 옷이 구겨졌을 때 다리미로 다림질해요 (“When the clothes are wrinkled, I iron them.”)
• 옷이 구겨지면 다리미로 다림질해요 (“If/when the clothes get wrinkled, I iron them.”)

The nuance is subtle: -으면 feels more like a general rule or condition, while -었을 때 pinpoints the moment it’s already wrinkled.

Why is 옷이 marked with the subject particle -이 instead of the object particle -을?

Because 구겨지다 is passive/intransitive: the clothes themselves undergo the action of getting wrinkled. In Korean, the undergoer of a passive verb is treated as the grammatical subject, so it takes -이/가. If you used an active verb like 다리다 (“to iron”), you would mark 옷 with -을 (e.g., 옷을 다려요).

What does the particle -로 indicate in 다리미로 다림질해요?

The particle -로 marks the instrument or means by which an action is done. So 다리미로 means “with (an) iron” or “using an iron.”

Can we say 다리미로 옷을 다려요 instead of 다리미로 다림질해요? What’s the difference?

Yes, you can.
• 다려요 comes from 다리다, a native Korean verb meaning “to iron.” You would say 다리미로 옷을 다려요 (“I iron clothes with an iron”).
• 다림질해요 is the verb 다림질하다 (다림질 + 하다 = “to do ironing”).
Both are correct; 다림질하다 is very common in everyday speech and writing, while 다리다 is slightly more direct but less formal.

Why is 옷을 omitted in 다림질해요?

Korean often drops the object when it’s obvious from context. Since you just mentioned 옷 in the first clause, you don’t need to repeat 옷을 before 다림질해요—listeners already know you’re ironing the clothes.

Why is 다림질해요 in the present tense instead of the past or future?

The sentence describes a habitual or routine action: “When clothes get wrinkled, I iron them.” In Korean, you use the present tense (-해요) to talk about regular habits or general truths.