Learn Hardcore Korean: eotteohge pyeonjireul sseoya hae?

편지 is the direct object (the thing being written). Korean marks direct objects with -를 (after a vowel) or -을 (after a consonant) to show what the verb acts on.

What does 써야 해 mean? Why not just 써?

써야 해 expresses obligation or necessity. It breaks down as: • 써- (verb stem of 쓰다, “to write”)
• -야 (connective ending, “must/have to”)
• 해 (casual form of 하다, “to do”)
So 써야 해 means (I/you/we) must write, not just “write.”

Why is there no subject like 내가 in the sentence?

Korean often omits subjects (and objects) when they’re clear from context. Here, it’s understood who needs to write, so 내가 (“I”) isn’t necessary.

What tense and politeness level is 써야 해?

This is present tense with a casual/informal ending. For other levels: • Polite: 어떻게 편지를 써야 해요?
• Formal: 어떻게 편지를 써야 합니까?

What’s the difference between 써야 해 and 써야 돼?

Both mean must write or have to write.
• 써야 해 comes from 해야 하다 (“have to do”).
• 써야 돼 comes from 해야 되다 (also “have to do”).
There’s no major difference in meaning—just a slight variation in everyday speech.

How can I make this sentence more respectful toward the listener?

You can use the honorific verb 쓰시다: • Polite honorific: 어떻게 편지를 쓰셔야 해요?
• Formal honorific: 어떻게 편지를 쓰셔야 합니까?

Can I rephrase it as 어떻게 편지를 쓰면 돼? Is the nuance different?

Yes. -으면 되다 (e.g. 쓰면 돼) asks “What should I do so that it’s okay?” rather than emphasizing obligation.
• 써야 해 → stresses necessity (“I must write”).
• 쓰면 돼 → focuses on the steps or method that will work. Both are common in conversation.