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‘-을/ㄹ 때’ is used to show the moment when a certain event happens or a certain action/state is continuing. It is placed after a verb or adjective word stem. If the stem ends with a consonant, use ‘-을 때’. When the stem ends with a vowel or ‘ㄹ’, use ‘-ㄹ 때’.
● 가족하고 함께 있을 때 행복해요. (I am happy when I’m with my family.)
● 저는 공부할 때 음악을 들어요. (I listen to music when I study.)
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‘못 -‘ is used to show an action is not possible or the action is not well-done. It isn’t used in adjectives, imperative and propositive sentences. It can also be used with ‘-지 못하다‘. When the verb is ‘~하다’ form like ‘공부하다‘, ’못‘ comes between ‘~’ and ‘하다’ like ‘공부 못하다’.
● 시끄러워서 못 잤어요. (I couldn’t sleep because it’s too noisy.)
● 저는 요리를 못해요. (I can’t cook well.)
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‘-으면/면, -이면’ is used for conditional statements, equivalent to ‘if’ in English. When the verb stem ends with a consonant, use ‘으면’. When the verb stem ends with a vowel or ‘ㄹ’, use ‘면’.
● 비가 오면 집에서 쉬겠어요. (If it rains today, I will rest at home.)
● 질문이 있으면 언제든지 물어 보세요. (If you have a question, ask me anytime.)
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‘-을/ㄹ 수 있다’ is used to show the ability to do something or the possibility of something happened. ‘-을/ㄹ 수 있다’ is its negative form. When the word stem ends with a consonant, use ‘을 수 있다’’. When the word stem ends with a vowel or ‘ㄹ’, use ‘ㄹ 수 있다’’.
● 저는 운전을 할 수 있어요. (I can drive a car.)
● 배가 아파서 점심을 먹을 수 없었어요. (I couldn’t eat lunch because of the stomachache.)
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‘- 동안’ is used after a noun which refers a certain period of time. It shows how a certain action or state continues in time.
● 저는 어제 여섯 시간 동안 잤어요. (I slept for 6 hours yesterday.)
● 한 달 동안 한국어를 공부했어요. (I studied Korean for one month.)
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‘-는군요, -군요’ is used to express surprise, delight, or wonder. Although often taught in most text books, this grammar pattern is not used frequently except in formal situations. A more commonly used grammar pattern with the same usage is ‘-는구나, -구나’. For the past tense, ‘-었군요/았군요/였군요’ is used.
● 날씨가 정말 좋군요! (The weather is really nice!)
● 노래를 정말 잘하는군요! (You are such a wonderful singer!)
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‘-기 전에’ is attached to a verb stem to give the meaning of ‘before’. ‘- 전에’ is attached to a noun to give the same meaning.
● 방을 청소하기 전에 창문을 여세요. (Open the window before cleaning the room.)
● 두 달 전에 가방을 샀어요. (I bought a bag two month ago.)
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1) This grammar can be used for providing the background for some further consideration which may or may not be stated.
● 가 : 오늘 저녁에 시간 있어요?나 : 네, 있는데요. (왜요?)
2) It can be used for Turing down a proposal politely or showing reservation about something.
● 가 : 좀 도와 주세요.나 : 제가 좀 바쁜데요.
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‘-이나/나’ is like ‘(either) N or’. When the noun ends with a vowel, use ‘이나‘. When the noun ends with a consonant, use ‘나’.
● 버스나 지하철을 타세요. (Take a bus or subway.)
● 집이나 사무실로 연락 주세요. (Give me a call at home or at my office.)
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To express that an action or the result of an action is continuous, add ‘-고 있다’ to the end of the verb stem.
● 저는 집에 가고 있어요. (I am going home.)
● 지금 뭐 하고 있어요? (What are you doing now?)
● 오늘 아침 7시에는 밥을 먹고 있었어요. (I was eating breakfast at 7 a.m. today)