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gwajereul geumyoilkkaji kkeutnaeya hae.

과제를 금요일까지 끝내야 해.gwajereul geumyoilkkaji kkeutnaeya hae.
I have to finish the assignment by Friday.
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Questions & Answers about gwajereul geumyoilkkaji kkeutnaeya hae.

What does the ending -아/어야 해 express in this sentence?

The ending -아/어야 해 attaches to a verb stem (here, 끝내 from 끝내다) to express obligation or necessity. In English it’s like saying “have to” or “must.”

  • Verb stem + -아/어야 해 = “You have to [verb].”
  • Since 끝내다 ends in a vowel plus -다, you use -아야 해, making 끝내야 해 = “(I) have to finish.”
Why is 금요일까지 used instead of just 금요일에?

-까지 means “until” or “by.” It sets a deadline.

  • 금요일에 끝내야 해 would mean “I have to finish on Friday” (implying sometime during Friday).
  • 금요일까지 끝내야 해 means “I have to finish by Friday” (anytime up to and including Friday).
Can I say 끝내야 돼 instead of 끝내야 해?

Yes. -아/어야 되다 is another common way to express obligation, parallel to -아/어야 하다.

  • Informal: 끝내야 돼 (casual speech)
  • Polite: 끝내야 돼요 or 끝내야 해요
What is the difference between -아/어야 해 and -아/어야 돼?

There’s no major difference in meaning—they both express “must.” Differences are mostly in style and region:

  • -아/어야 해 is slightly more formal or neutral.
  • -아/어야 돼 can sound more colloquial.
    Speakers often choose based on personal habit or the level of formality.
How would you make this sentence more polite or formal?

You can add 요 at the end or use the formal polite form of 하다:

  • Polite: 과제를 금요일까지 끝내야 해요.
  • Formal: 과제를 금요일까지 끝내야 합니다.
Why is there no subject in the sentence? Who is doing the action?

Korean often omits the subject when it’s clear from context. Here “I” (or “we”) is implied. If you need to specify:

  • 나는 과제를 금요일까지 끝내야 해. (I have to finish the assignment by Friday.)
Could I use a different verb instead of 끝내다 to mean “finish”?

Yes. Some alternatives:

  • 마치다: 과제를 금요일까지 마쳐야 해.
  • 완성하다 (to complete): 과제를 금요일까지 완성해야 해.
    Choose based on nuance: 끝내다/마치다 is common for general “finish,” while 완성하다 often implies a more thorough “completion.”
How do I change this sentence to past tense, like “I had to finish the assignment by Friday”?

Change -아/어야 해 into its past form -아/어야 했어 (informal) or -아/어야 했어요 (polite):

  • Informal: 과제를 금요일까지 끝내야 했어.
  • Polite: 과제를 금요일까지 끝내야 했어요.