안녕하세요! So first of all there is actually a difference between 좋아 and 촣아해~ The former is an adjective and it means "good." The latter is a verb and the one should be using; it means "to like." Next, by adding 요, then yes it makes it formal. Omitting the요 makes it informal. When you choose which depends on who talk to and how close you are to them. The phrases: "Yes, I don't like coffee." -> " 네, 커피 안좋아해요." Also, no, if you reply 아니요 you are saying " no, I do like coffee." "커피 좋아" is perfectly natural, but it means "coffee is good." I guess you could say "네, 커피 좋아" but you are just describing coffee , so its an indirect way to say that you like coffee lol. I guess this is kind of confusing hahaha Hope this is helpful! 화이팅!!!~^^

커피 안 좋아해요? it means "You don't like coffee?" And it's written in formal way (?) - YES So as a reply i'd like to say "No I don't like coffee" rather than saying 네(Yes) I'd like to say something longer like 'I don't like coffee' - 네. 커피 안 좋아해요. Is 커피 안 좋아 informal? will adding 요 make it formal or will it sound unnatural? - 커피 안 좋아해? (informal, natural) 커피 안 좋아해요? (formal) < 커피 안 좋아하세요? (more formal) < 커피 안 좋아하십니까 (rarely used) Additional Details: Also 커피 좋아 is 'I like coffee' or does it sound unnatural? 커피 좋아해. 커피 좋아해요. sounds natural. 커피 좋아 sounds childish like a baby talk or talking oneself. But it can be said naturally when you are excited. eg. your friend said, "Would you like coffee? 커피 마실래? " "커피, 좋아!" but in this case, that dosen't express your favorite, it means your agreement like "good, excellent" Additional Details: By replying with "아니요" am i saying I like coffee? When you like coffee, Q: 커피 좋아해요? - A 네. 좋아해요. Q: 커피 안 좋아해요? - A 아니요. 좋아해요.

You are correct – 커피(를) 안 좋아해요? means “You don’t like coffee?” I would like to point out that there is a difference between being formal (or informal) and polite (or impolite/rude). 먹어 – informal and potentially rude (if used improperly) 먹어요 – informal but polite 먹습니다 – formal 좋아해요 therefore is informal but still polite – perfect for most situations in Korean, and a safe bet for a foreign learner of the language to use. On the other hand, 좋아해 is both informal and impolite and should be used with caution – to children, to animals, to yourself, or to others below you status-wise. Otherwise, it will sound rude. I mean look at who it’s meant to be spoken to – using it with the president of a company would be like treating him as if he were a child, animal, or unimportant person. --- Replying with 네 would be incorrect, as it would mean you were agreeing with the speaker and that you do not like coffee after all. There’s nothing wrong with just answering yes or no, restating the question, or restating the question with natural omissions. It might seem boring when learning a foreign language, but it’s quite natural. You don’t always need a long, elaborate answer. I mean, natives don’t answer that way. It’s just because you’re learning and you want to use what you know and not just sound like you’re copying or clueless. But truth is, sometimes that’s just the way a good response goes  You could respond “아니요”; “아니요, 커피(를) 안 좋아해요”; “아니요, 안 좋아해요”; “아니요, 안 좋아요.” I would pick the third one  or just the first haha.

In Korean, it is best not to think of there as being a "yes" and "no". Instead, you should think of 네 as being a sign of agreement or confirmation and 아니요 being the opposite (disagreeing or cancelling out the statement). So therefore you are correct - responding to "커피 안 좋아해요?" (You don't like coffee?) with 아니요 means you disagree with this statement and that you do, in fact, like coffee. This is a much better design than in English, where "yes" and "no" are ambiguous at times and can mean either agreement or disagreement. ex. You don't play sports? a) Yes (I don't play sports) b) No, I do play sports. c) No (you're right), I don't play sports. All of these answers are correct, but without clarifying, just saying "yes" or "no" would be confusing. ("No" you do play sports or "no" you don't play sports? would be a common question for a speaker to ask to clarify the answer.)

Again, worry less about formality and more about politeness. Adding 요 does not make anything “formal”, it makes it “polite”. Don’t worry so much about terminology though. Focus on the ending and when it’s used. 커피(가) 안 좋아 is informal and impolite. Adding 요 would hardly make it unnatural. It’s perfectly natural to be polite  --- I think you should realize that there’s a difference between 좋아해(요) and 좋아(요). 좋아해요 means “likes” and 좋아요 means “is good”. 좋아요 can mean “like” though indirectly. Each of these words uses a different grammar pattern: 좋아해요 -> 저는 사과를 좋아해요 (은/는 을/를) 좋아요 -> 저는 사과가 좋아요 (은/는 이/가) While the second sentence literally means “As for me, apples are good”, this is obviously unnatural sounding in English and is therefore better translated as “I like apples” because the meaning in this context is the same. 날씨가 좋아요: The weather is good (o) 날씨가 좋아해요: The weather is good (x) 날씨를 좋아해요: (Someone) likes the weather (o) So 커피 좋아 technically means “coffee is good”, but Korean is highly contextual and it will be clear that the meaning is “as for me, coffee is good” aka “I like coffee”. However, it is probably a rude response and should be changed to 좋아요.