(I found that) - ~던데

던데 is used when you found that something was contrary to my previous opinion/expectation or opinions/expectations of others.

For example,

• 이미 하던데 = (I found that they) were already doing it

Replace 다 of verbs/adjectives with 던데

• 하던데 = (I found that he/she/they) was/were doing it
• 가던데 = (I found that he/she/they) was/were going (somewhere)
• 오던데 = (I found that he/she/they) was/were coming (here)
• 먹던데 = (I found that he/she/they) was/were eating
• 마시던데 = (I found that he/she/they) was/were drinking 
• 살던데 = (I found that he/she/they) was/were living (somewhere) 

There is / I have - 있다/있네

있다 is used colloquially to mean "There is/are" or "I have."

For example,

• 저기에 호수 있다 = There is a lake over there.

• 나 갤럭시 에스 쓰리 있다 = I have a Galaxy S3.

Similarly, you could also use "있네" to mean "There is/are" or "I have."

However, 있네 is used when you did not have any prior knowledge of the presence of something or having owned something.

• 저기에 호수 있네 = There is a lake over there. (I didn't know there was a lake over there.)

• 어, 나 지갑 있네 = Oh, I have a wallet. (I thought I didn't have/bring it.)

I heard / You said - ~며

며 can mean "I heard" or "You said."

The meaning of 며 depends on the context, i.e. what sentence follows next.

For example,

• 정수야, 서울에 간다며? 잘 갔다와.
• = Hey, Jeong-su, I heard you're going to Seoul. Have a nice trip!

• 정수야, 서울에 간다며. 아직 안갔어?
• = Hey, Jeong-su, you said you're going to Seoul. You haven't left yet? 

Add 며 to verbs / adjectives.

한다 (present written form) + 며 = 한다며 = You said you'd do

• 간다며 = I heard you go (are going) / You said you go (are going)
• 온다며 = I heard you come / You said you come
• 먹는다며 = I heard you eat / You said you eat
• 마신다며 = I heard you drink / You said you drink
• 잔다며 = I heard you sleep / You said you sleep
• 일어난다며 = I heard you wake up / get up // You said you wake up / get up
• 논다며 = I heard you play / have fun // You'd said you play / have fun

I used to do - 하던

하던 means "used to" or it refers to an action or state in the past.

A noun is usually followed by 하던 which describes the noun.

e.g. 여기는 내가 일하던 곳이야 = This is the place where I used to work / had worked.


The past tense form of '하던' is 했던 and it means essentially the same as 하던 when used in this sense.

e.g. 여기는 내가 일하던 곳이야 = 여기는 내가 일했던 곳이야 = This is the place where I used to work / had worked.

I used to do - 했었어

었어 is used with verbs and adjectives to mean "used to".

Informal	Written Form	Spoken Form
Positive	했었다	했었어
Negative	하지 않았었다 안 했었다	하지 않았었어 안 했었어

* The letters in bold are used more commonly in each corresponding form.

Replace 다 in verbs in their past tense with 었다

• 갔다 → 갔었다 = used to go
• 안갔다 → 안갔었다 = used to not go
• 왔다 → 왔었다 = used to come
• 먹었다 → 먹었었다 = used to eat
• 마셨다 → 마셨었다 = used to drink
• 좋아했다 → 좋아했었다 = used to like
• 싫어했다 → 싫어했었다 = used to hate 
• 봤다 → 봤었다 = used to watch
• 들었다 → 들었었다 = used to listen 
• 읽었다 → 읽었었다 = used to read
• 썼다 → 썼었다 = used to write / use
• 살았다 → 살았었다 = used to live
• 샀다 → 샀었다 = used to buy

Example sentences

• (예전에) 서울 중학교를 다녔었어 = I used to attend/go to Seoul Middle School (before/in the past).
  
• 예전에는 버섯을 좋아했었어 = I used to like mushrooms in the past. *(but not now)
• 2년전에 영국에서 살았었어 = I used to live in England 2 years ago.
  
• 초등학생 때는 소설책을 많이 읽었었어 = I used to read a lot of novels when I was a primary school student.
• 예전에는 버스를 많이 탔었는데, 지금은 지하철을 더 많이 이용해 = I used to ride a bus a lot but now I use the subway more.

The same apples to adjectives

• 좋았다 → 좋았었다 = (it) used to be good
• 안 좋았다 → 안 좋았었다 = used to be not good 
• 컸다 → 컸었다 = used to be big / large *
• 작았다 → 작았었다 = used to be small
• 높았다 → 높았었다 = used to be tall **
• 많았다 → 많았었다 = (there) used to be a lot / many
• 적었다 → 적었었다 = used to be few/little (in quantity)

* 크다/컸다/컸었다 can also mean "tall" when used to refer to height of a person or animals.

• E.g. 키가 컸었다 = used to be tall (키 = height)

** 높다/높았다/높았었다 is used for objects only such as buildings, mountains or sky.

• E.g. 엠파이어 스테이트 빌딩은 다른 빌딩들이 세워지기 전까지 뉴욕에서 가장 높았었다 = The Empire State Building used to be the tallest building in New York City before other buildings were built.

Example Sentences

• 오전에는 주차장에 차들이 많았었는데, 지금은 되게 적네 = There used to be a lot of cars in the car park but now there are only a few. (되게 적네 = very few / little)
  
• 이 사과나무는 5년전만 해도 내 키보다 작았었는데, 지금은 우리 집보다 더 커 = This apple tree used to smaller than my height but now it's bigger (taller) than our house.

Polite Form

Polite	Written Form	Spoken Form
Positive	했었습니다	했었어요
Negative	안 했었습니다 하지 않았었습니다	안 했었어요 하지 않았었어요

 

• 어렸을 때는 버섯을 싫어했었는데, 지금은 잘 먹어요 = I used to hate mushrooms when I was young but now I eat them well.
• 겨울에는 나무에 잎이 하나도 없었는데, 지금은 많아요 = There used to be no leaves on trees, but now there are many / a lot of /a plenty of leaves.
• 작년에는 시골로 여행을 자주 갔었어요 = I used to travel to countrysides often last year.

• 부산에 가면 떡을 자주 사먹었어요 = When I go to Busan, I used to buy and eat rice cakes quite often.*
• 예전에는 연필로 많이 썼었는데, 지금은 펜을 더 많이 사용해요 = I used to write with a pencil a lot but now I use a pen more often.
• 예전에는 팝뮤직만 들었었는데, 지금은 클래식도 듣고, 다른 예전 노래들도 들어요. = I used to only listen to pop music but now I also listen to classics and other songs of the past. 
• 더운 여름에 시원한 개울가에 자주 놀러갔었어요 = When it was hot in summer, we used to go to a cool stream/brook and play around there. **

* 사먹다 = buy and eat
** 놀러가다 = to go and play

Are we doing? - 하는 거야 / 거예요?

Are we doing? - 하는 거야 / 거예요?

하는 거야/ 거예요? is usually used when you want to ask someone what you (both singular and plural) are doing, or will be doing immediately.

For example, when you are in a group of people who are doing things as a group, and you want to ask a leader of the group what you all will be doing.

우리 저기 가는 거야? = Are we going there? [Informal]
우리 저기 가는 거예요? = Are we going there? [Polite]

Note: 하는 거야? = Are you/we doing?  
HOWEVER, the polite form of "Are you doing?" usually uses "시는 거예요?" whereas the polite form of "Are we doing?" uses "는 거예요?"
See Are you doing? - ~는 거야? , Are you doing? - ~시는 거예요?

● Rule 

Take 다 off a plain verb and add 는 거야 / 거예요?

• 하다 → 하는 거야 / 거예요? = Are we doing?
• 가다 → 가는 거야 / 거예요? = Are we going?
• 읽다 → 읽는 거야 / 거예요? = Are we reading?
• 보다 → 보는 거야 / 거예요? = Are we watching?
• 쓰다 → 쓰는 거야 / 거예요? = Are we writing?
• 먹다 → 먹는 거야 / 거예요? = Are we eating?
• 마시다 → 마시는 거야 / 거예요? = Are we drinking?
• 자다 → 자는 거야 / 거예요? = Are we sleeping?
• 보내다 → 보내는 거야 / 거예요? = Are we sending?

Example Sentences

• 운동 하는 거예요? = Are (we) exercising?
• 저기로 가는 거예요? = Are (we) going there?
• 이 차로 가는 거예요? = Are (we) going by this car?
• 이거 먹는 거예요? = Are (we) eating this?
• 이걸로 먹는 거예요? = Are (we) eating with this?
• 여기서 자는 거예요? = Are (we) sleeping here?
• 오늘 저 영화 보는 거예요? = Are (we) watching that movie today?
• 이걸로 보는 거예요? =  Are (we) watching with this?

You can add 언제, 어디, 누가, 뭐, 어떻게 or 왜 [when, where, who, what, how or why] in front of ~시는 거예요? to make these sentences.

• 오늘 우리 뭐 하는 거예요? = What are we doing today?
• 뭐 읽는 거예요? = What are (we) reading?
• 뭐 보는 거예요? = What are (we) watching?
• 뭐 쓰는 거예요? = What are (we) writing?
• 뭐 먹는 거예요? = What are (we) eating?
• 뭐 마시는 거예요? = What are (we) drinking?
• 뭐 보내는 거예요? = What are (we) sending?
• 어디 가는 거예요? = Where are (we) going?
• 어디서 자는 거예요? = Where are (we) sleeping?
• 누가 하는 거예요? = Who is doing?
• 어떻게 쓰는 거예요? = How are (we) writing?
  
• 왜 하는 거예요? = Why are (we) doing?

More Example Sentences

• 우리 어디 가는 거예요? = Where are we going?
• 아, 지금 시내에 가는 거예요. = Ah, we're going to the city.
• 이 차로 가는 거예요? = Are (we) going by this car?
• 네, 어서 타세요. = Yes, please get in.
• 뭐 먹을 거예요? = What will we eat?  Verbs - Future [Will]
• 스파게티 먹을 거예요. 스파게티 좋아하세요? = We will eat spaghetti. Do you like it?
• 네, 좋아해요. = Yes, I like it.

I think / It seems - 하는 거 같애 (General)

I think / It seems - 하는 거 같애/같아 (General)

하는 거 같애 means "I think he/she/they is/are doing (something)" or "It seems he/she/they are doing (something)."
Please note that although grammatically 하는 거 같아 is right. In spoken Korean, it's usually pronounced 하는 거 같애.


[Verbs]

Written Form	Present	Past
Positive	하는 것 같다	했던 것 같다
Negative	하지 않는 것 같다 안하는 것 같다	하지 않았던 것 같다 안했던 것 같다

Spoken Form	Present	Past
Positive	하는 거 같애	했던 거 같애
Negative	하지 않는 거 같애 안하는 거 같애	하지 않았던 거 같애 안했던 거 같애

Note: In written Korean, it is written 하는 것 같다 whereas in spoken Korean, it is spoken as 하는 거 같애. It is mostly likely due to the fact that 것 is a lot more cumbersome to pronounce than 거 when speaking.


Rules
 
1. Take 다 off a plain form of verbs and attach 는 거 같애/지 않는 거 같애 etc. to it.
2. Drop ㄹ off a plain form of verbs that have ㄹ as a final consonant.
3. Take 다 off a past tense form of verbs and attach 던 것 같다/던 거 같애 etc. to it.

• 하다 → 하는 거 같애 = I think they do / It seems they do
• 먹다 → 먹는 거 같애 = I think they eat / It seems they eat
  
• 일어나다 → 일어나는 거 같애 = I think they get up
  
• 자다 → 자는 거 같애 = I think they sleep
  
• 보다 → 보는 거 같애 = I think they watch
  
• 씻다 → 씻는 거 같애 = I think they wash
  
• 달리다 → 달리는 거 같애 = I think they run
  
• 놀다 → 노는 거 같애 = I think they muck around
  
• 살다 → 사는 거 같애 = I think they live
  

• 했다 → 했던 거 같애 = I think they did
  
• 먹었다 → 먹었던 거 같애 = I think they ate
  
• 봤다 → 봤던 거 같애 = I think they watched
  
• 살았다 → 살았던 거 같애 = I think they lived
  
• 놀았다 → 놀았던 거 같애 = I think they mucked around
  

Example Sentences

• 저기서 사람들이 축구 하는 거 같애 = I think people are playing soccer over there.
  
• 이 개는 저 개집에서 살았던 거 같애 = I think this dog lived in that kennel. = I think this dog used to live in that kennel.
• 저 방에는 아기가 자고 있는 거 같애 = I think a baby is sleeping in that room.
• 나는 밥을 빨리 안먹는 거 같애 = I think I don't eat (a meal) fast.

[Adjectives]

Written Form	Present	Past
Positive	좋은 것 같다	좋았던 것 같다
Negative	좋지 않은 것 같다 안좋은 것 같다	좋지 않았던 것 같다 안좋았던 것 같다

Spoken Form	Present	Past
Positive	좋은 거 같애	좋았던 거 같애
Negative	좋지 않은 거 같애 안좋은 거 같애	좋지 않았던 거 같애 안좋았던 거 같애

Rules

1. Attach a descriptive form of adjectives to 거 같애.
2. Take 다 off a past tense form of adjectives and attach 었던 거 같애.

• 좋은 → 좋은 거 같애 = I think it's good / It seems good
• 많은 → 많은거 같애 = I think there's a lot / There seems a lot
  
• 큰 → 큰 거 같애 = I think it's big / It seems big
  
• 작은 → 작은 거 같애 = I think it's small / It seems small
  
• 예쁜 → 예쁜 거 같애 = I think it's pretty / It seems pretty
  
• 똑똑한 → 똑똑한 거 같애 = I think he's clever / He seems clever
  
• 솔직한 → 솔직한 거 같애 = I think she's honest / She seems honest
• 좋았다 → 좋았던 거 같애 = I think it was good / It seemed good
  

• 맛있었다 → 맛있었던 거 같애 = I think it was delicious
  
• 재밌었다 → 재밌었던 거 같애 = I think it was fun
  
• 쉬웠다 → 쉬웠던 거 같애 = I think it was easy
  
• 많았다 → 많았던 거 같애 = I think there was a lot

Example sentences

• 태국음식은 맛있는 거 같애 = I think Thai food is delicious
• 이 집은 굉장히 큰 거 같애 = I think this house is enormously big.
• 이번 수학시험은 정말 쉬웠던 거 같애 = I think the maths test was really easy.
• 내 기억에 저 들 위에는 꽃들이 많았던 거 같애 = According to my memory, I think there were a lot of flowers on that hill.

[Nouns]

Written Form	Present	Past
Positive	고양이인 것 같다	고양이였던 것 같다
Negative	고양이가 아닌 것 같다	고양이가 아니었던 것 같다

Spoken Form	Present	Past
Positive	고양이(인 거) 같애	고양이였던 거 같애
Negative	고양이(가) 아닌 거 같애	고양이(가) 아니었던 거 같애

Note: The object particle, 가/이, is usually omitted in spoken Korean. 인 거 is also usually omitted.

같다's original meaning is "look like." Therefore, 같애 phrases can have alternative translations but essentially they mean the same thing.

• 하는 거 같애 = I think they're doing. It looks like they're doing.
• 예쁜 거 같애 = I think it's pretty. It looks pretty.
  
• 치킨인거 같애 = I think it's a chicken. It looks like a chicken (food).
  

Rules

Attach 인 것 같다/였던 것 같다/인 거 같애/였던 거 같애 to a noun.

• 강아지(인 거) 같애 = I think it's a puppy (It looks like a puppy)
  
• 고양이(인 거) 같애 = I think it's a cat
  
• 뻐꾸기(인 거) 같애 = I think it's a cuckoo
  
• 나무(인 거) 같애 = I think it's a tree
• 사람(인 거) 같애 = I think it's a person
  
• 학교(인 거) 같애 = I think it's a school

Example sentences

• 민희: 너 저 동물이 뭔지 알아? = Do you know what that animal is?
• 수영: 저건 사자 같애. = I think that is a lion. (That looks like a lion)
  
• 민희: 사자 아닌 거 같은데. 호랑이 같애. = I don't think that is a lion. I think it's a tiger.
• 수영: 그런가? 그럼 저 멀리 저건 뭐지? = Is it? Then what is that over there afar? 
• 민희: 사람은 아닌 거 같애. 동물인 거 같애. = I don't think it's a human. I think it's an animal.
  
• 수영: 침팬지다. = It's a chimpanzee.
• 민희: 침팬지 같았어. = I thought that was a chimpanzee. (It looked like a chimpanzee)
  

Note: 같다's past tense is 같았어 and so 고양이 같았어 = I thought it was a cat.


Formal Forms

Rules  

Written Korean = Change 다 to 습니다.
Spoken Korean = Attach 요 to the end of a sentence. 
eg.

• 태국음식은 맛있는 것 같습니다 = I think Thai food is delicious
• 이 집은 굉장히 큰 거 같애요 = I think this house is enormously big.
• 이번 수학시험은 정말 쉬웠던 거 같애요 = I think the maths test was really easy.
• 내 기억에 저 들 위에는 꽃들이 많았던 거 같애요 = According to my memory, I think there were a lot of flowers on that hill.

They/he/she think(s) = ~ 같대

같대 is a shortened form of 같다고 해 and it is used to express what they/he/she think(s). 같대 is usually used in spoken Korean. Attach 요 to 같대 to make it formal.

• 할머니가 이 개는 저 개집에서 살았던 거 같대 = Grandma thinks this dog lived in that kennel. = Grandma thinks this dog used to live in that kennel.
• 엄마가 저 방에는 아기가 자고 있는 거 같대 = Mum thinks a baby is sleeping in that room.
• 친구가 나는 밥을 빨리 먹는 거 같대요 = My friend thinks I eat (a meal) fast.

• 폴이 태국음식은 맛있는 거 같대 = Paul thinks Thai food is delicious
• 동생의 기억엔 저 들 위에는 꽃들이 많았던 거 같대요 = According to my younger (brother/sister)'s memory, He/she thinks there were a lot of flowers on that hill.

• 강아지(인 거) 같대 = They/he/she think(s) it's a puppy (It looks like a puppy)
• 고양이(인 거) 같대요 = They/he/she think(s) it's a cat

Allowed to - 해도 된다

Allowed to - 해도 된다 

Informal Form

Informal	are allowed to	were allowed to
Written	해도 된다	해도 됐었다
Spoken	해도 돼	해도 됐었어

Informal	aren't allowed to	weren't allowed to
Written	하면 안된다	하면 안됐었다
Spoken	하면 안돼	하면 안됐었어

Note:

해도 돼 means "allowed to do" and 안해도 돼 means "don't have to do," NOT "not allowed to do." This needs some explanations.

First of all, 돼 means "ok or allowed." 해도 돼 literally means "doing is ok." 안해도 literally means "not doing" therefore 안해도 돼 literally means "not doing is ok" which means "don't have to do."

하면 안돼 means "not allowed to do." 하면 literally means "if I do" and 안돼 means "not ok" therefore 하면 안돼 literally means "if I do it, it's not ok" which can be expressed as "not allowed to do"

Compare this with Have to - 해야 한다

However, you don't have to know these explanations to use them. Actually, I've never thought about why these mean what they mean until today. The best way to learn them is to use them frequently until they become memorised.

Rules 

1. Attach 도 된다/도 됐었다/도 돼/도 됐었어 to the positive informal spoken form of verbs Verbs - Present, Past 

• 해 → 해도 된다 = allowed to do
  
• 가 → 가도 된다 = allowed to go
  
• 봐 → 봐도 된다 = allowed to see
  
• 들어 → 들어도 된다 = allowed to hear
• 먹어 → 먹어도 된다 = allowed to eat
  
• 마셔 → 마셔도 된다 = allowed to drink
• 달려 → 달려도 된다 = allowed to run
  
• 앉아 → 앉아도 된다 = allowed to sit
  
• 놀아 → 놀아도 된다 = allowed to play/muck around

2a. Take 다 off a plain form of verbs without a final consonant and attach 면 안된다/면 안됐었다/면 안돼/면 안됐었어 to it. (Includes verbs with ㄹ as a final consonant)

• 하다 → 하면 안된다 = aren't allowed to do
  
• 가다 → 가면 안된다 = aren't allowed to go
• 춤추다 → 춤추면 안된다 = aren't allowed to dance
  
• 놀다 → 놀면 안된다 = aren't allowed to play/muck around
  
• 밀다 → 밀면 안된다 = aren't allowed to push
  
• 돌다 → 돌면 안된다 = aren't allowed to spin

2b. Take 다 off a plain form of verbs with a final consonant and attach 으면 안된다/으면 안됐었다/으면 안돼/으면 안됐었어 to it.

• 먹다 → 먹으면 안된다 = aren't allowed to eat
  
• 앉다 → 앉으면 안된다 = aren't allowed to sit
  
• 숨다 → 숨으면 안된다 = aren't allowed to hide
  
• 잡다 → 잡으면 안된다 = aren't allowed to catch
  
• 집다 → 집으면 안된다 = aren't allowed to pick up
  
• 접다 → 접으면 안된다 = aren't allowed to fold

Exceptions

• 듣다 → 들으면 안된다 = aren't allowed to listen
• 걷다 → 걸으면 안된다 = aren't allowed to walk
  

Example sentences
Written form

• 부페에서는 먹고 싶은 만큼 먹어도 된다 = At a buffet (restaurant), people are allowed to eat as much as they want.
• 시험을 마친 사람은 집에 가도 된다 = Those who have finished the exam can go home.
  
• 도서관에서는 크게 얘기하면 안된다. = It is not allowed to speak loudly in the library.
  
• 신생아들은 딱딱한 음식을 먹으면 안된다. = Infants are not allowed to eat solid food.
• 작년까지 학생들은 매점 자판기를 사용해도 됐었다 = Until last year, students were allowed to use a stall vending machine.

Spoken form

• TV 봐도 돼 = You are allowed to watch TV. (You can watch TV.)
• 이 케잌 먹어도 돼 = You are allowed to eat this cake. (You can eat this cake,)
• 술과 담배는 사면 안돼 = You are not allowed to buy alcohol and tobacco.
• 어제까지 놀아도 됐었어 = Until yesterday, I was allowed to muck around.
• 작년까지 빅토리아공원에는 들어가면 안됐었어 = Until last year, people were not allowed to enter the Victoria park.
  

Formal Form

Formal	are allowed to	were allowed to
Written	해도 됩니다	해도 됐었습니다
Spoken	해도 돼요	해도 됐었어요

Formal	aren't allowed to	weren't allowed to
Written	하면 안됩니다	하면 안됐었습니다
Spoken	하면 안돼요	하면 안됐었어요

Note: The rules are the same as above.

Example sentences
Written form

• 부페에서는 먹고 싶은 만큼 먹어도 됩니다 = At a buffet (restaurant), people are allowed to eat as much as they want.
• 시험을 마친 사람은 집에 가도 됩니다 = Those who have finished the exam can go home.
  
• 도서관에서는 크게 얘기하면 안됩니다. = It is not allowed to speak loudly in the library.
  
• 신생아들은 딱딱한 음식을 먹으면 안됩니다. = Infants are not allowed to eat solid food.
• 작년까지 학생들은 매점 자판기를 사용해도 됐었습니다 = Until last year, students were allowed to use a stall vending machine.

Spoken form

• TV 봐도 돼요 = You are allowed to watch TV. (You can watch TV.)
• 이 케잌 먹어도 돼요 = You are allowed to eat this cake. (You can eat this cake,)
• 술과 담배는 사면 안돼요 = You are not allowed to buy alcohol and tobacco.
• 어제까지 놀아도 됐었어요 = Until yesterday, I was allowed to muck around.
• 작년까지 빅토리아공원에는 들어가면 안됐었어요 = Until last year, people were not allowed to enter the Victoria park.
  

Have to - 해야 한다

Have to - 해야 한다


Informal form

Informal	Have to	Had to
Written	해야 한다 해야 된다	해야 했다 해야 됐다
Spoken	해야 해 해야 돼	해야 했어 해야 됐어

Informal	Don't have to	Didn't have to
Written	하지 않아도 된다	하지 않아도 됐다
Spoken	하지 않아도 돼 안해도 돼	하지 않아도 됐어 안해도 됐어

Note: The words in bold are the more commonly used alternative of the two in each box.

Rules
1. Attach 야 한다/야 된다/야 돼/야 됐어 etc. to the informal spoken form of verbs. Verbs - Present, Past

• 해 → 해야 한다 = have to do
  
• 가 → 가야 한다 = have to go
  
• 와 → 와야 한다 = have to come
  
• 봐 → 봐야 한다 = have to see
  
• 먹어 → 먹어야 한다 = have to eat
  
• 마셔 → 마셔야 한다 = have to drink

2. Take 다 off a plain form of verbs and then attach 지 않아도 된다/지 않아도 됐다/지 않아도 돼 etc. to it.

• 하다 → 하지 않아도 된다 = don't have to do
  
• 가다 → 가지 않아도 된다 = don't have to go
  
• 오다 → 오지 않아도 된다 = don't have to come
  
• 보다 → 보지 않아도 된다 = don't have to see
  
• 먹다 → 먹지 않아도 된다 = don't have to eat
  
• 마시다 → 마시지 않아도 된다 = don't have to drink

3. Attach 안 and 도 돼/ 도 됐었어 to the front and back of the informal spoken form of verbs respectively. Verbs - Present, Past

• 안해도 돼 = don't have to do
  
• 안가도 돼 = don't have to go
  
• 안와도 돼 = don't have to come
  
• 안봐도 돼 = don't have to see
  
• 안먹어도 돼 = don't have to eat
  
• 안마셔도 돼 = don't have to drink

Example sentences
Written Form

• 성민은 오늘 서울에 가야 한다. = Seong-min has to go to Seoul today.
• 민주는 내일 학교에 가지 않아도 된다. = Min-ju doesn't have to go to school tomorrow.
• 애쉴리는 병때문에 작년 매일 약을 먹어야 했다 = Because of her sickness, Ashley had to take (lit. eat) medicine everyday last year.

Spoken Form

• 이번 주 목요일까지 과학 과제 끝내야 돼 = I have to finish the science assignment by this Thursday.
• 애쉴리는 이제 다 나아서 병원에 안가도 돼 = Because Ashley has been healed now, she doesn't have go to the hospital.
• 고추가 너무 매우면 안먹어도 돼 = If the chillies are too spicy, you don't have to eat them.
  

Formal form

Formal	Have to	Had to
Written	해야 합니다 해야 됩니다	해야 했습니다 해야 됐습니다
Spoken	해야 해요 해야 돼요	해야 했어요 해야 됐어요

Formal	Don't have to	Didn't have to
Written	하지 않아도 됩니다 안해도 됩니다	하지 않아도 됐습니다 안해도 됐습니다.
Spoken	하지 않아도 돼요 안해도 돼요	하지 않아도 됐어요 안해도 됐어요

Note: The rules for the conjugation are the same as above.


Example sentences
Written Form

• 성민은 오늘 서울에 가야 합니다. = Seong-min has to go to Seoul today.
• 민주는 내일 학교에 가지 않아도 됩니다. = Min-ju doesn't have to go to school tomorrow.
• 애쉴리는 병때문에 작년 매일 약을 먹어야 했습니다 = Because of her sickness, Ashley had to take (lit. eat) medicine everyday last year.

Spoken Form

• 이번 주 목요일까지 과학 과제 끝내야 돼요 = I have to finish the science assignment by this Thursday.
• 애쉴리는 이제 다 나아서 병원에 안가도 돼요 = Because Ashley has been healed now, she doesn't have go to the hospital.
• 고추가 너무 매우면 안먹어도 돼요 = If the chillies are too spicy, you don't have to eat them.

Source: Learn Korean: LP's Korean Grammar Guide

Imperatives

Imperatives - 해, 하지마

Imperative	Positive	Negative
Informal	해 가 먹어	하지마 가지마 먹지마
Formal	해요 가요 먹어요	하지마요 가지마요 먹지마요
Honorific	하세요 가세요 드세요	하지마세요 가지마세요 드시지마세요

The informal form is used among very close friends or when talking to a younger person who is very close to you in informal situations.

The formal form and the honorific form are used in formal situations. However, if I were to choose which one to use, I would choose the honorific form because the formal form is a bit casual-ish. It is safe to use the honorific form if you are unsure which one to use.

Note: The honorific form of verbs is present in Korean such as:

먹다 → 드시다 = eat
자다 → 주무시다 = sleep
죽다 → 돌아가시다 = die, pass away

먹어's honorific form is 드세요. It is usually used when talking to people above your age or in formal situations.

Rules

Informal positive (Imperative) = Present positive (spoken Korean)

• 해! = Do!
• 저리 가! = Go over there! (Leave me alone!)
• 이 과자 좀 먹어. = Eat some of these snacks.
• 물 좀 마셔. = Drink some water.

Informal negative = Take 다 off a plain form of verbs and attach 지마 to it.

• 가지마! = Don't go!
• 이 영화는 보지마! = Don't watch this movie!
• 이거는 먹지마. = Don't eat this.
• 이 책은 읽지마. = Don't read this book.

Formal positive and negative = Attach 요 to informal forms

Honorific positive = 
1. Take 다 off a plain form of verbs and then attach 세요 to verbs without a final consonant.
2. Attach 으세요 to verbs with a final consonant.
3. For verbs with a final consonant of ㄹ, drop it off and attach 세요 to it.

• 가세요! = Please go!
• 이리 오세요. = Please come here.
• 빨리 떠나세요! = Please leave quickly!
• 어서 드세요. = Please eat already.
• 물고기 손으로 잡으세요. = Please catch the fish with your hands.
  
• 손 흔드세요! = Please wave your hands! (흔들다 = wave)
  
• 빙글빙글 도세요! = Please turn round and round! (돌다 = turn round, spin)
  

Honorific negative = Take 다 off a plain form of verbs and attach 지마세요.

• 장난 하지 마세요! = Please don't fool around!
• 저 곳에는 가지 마세요. = Please don't go to that place. (Keep away from that place.)
• 박물관에 있는 물건들은 만지지 마세요. = Please don't touch things in the museum.

Comparatives & Superlatives

Comparatives [~보다]

~보다 is used to compare two persons or things. The person/thing that 보다 is referring to is the one that comes after "~er than" in English. The "~보다" phrase can also come before a subject. So the sentences below have the same meaning.

Note: 이/가 particles are more frequently used than 은/는 particles, and in the spoken Korean, almost exclusively 이/가 are used. 

• 나는 동생보다 키가 크다 = I am taller than (my) younger sibling.
• 내가 동생보다 키가 크다 = "I" am taller than (my) younger sibling.
• 동생보다 내가 키가 크다 = I am taller than (my) younger sibling.
• 동생보다 내가 키가 커 = I am taller than (my) younger sibling. [spoken form]
• 동생보다 제가 키가 커요 = I am taller than (my) younger sibling. [formal spoken form]

동생보다 = than younger sibling
동생 = younger sibling
키 = height
크다 = big
키가 크다 = tall
키가 작다 = short
나 = I
내 = 나 changes to 내 before 이/가
제 = the honorific form of 내 used in formal expressions

더 is usually added before an adjective. 더 = more

More examples

• 동물보다 사람이 더 똑똑하다 = Man is cleverer than an animal.
• 나일강이 아마존강보다 더 길다 = The Nile River is longer than the Amazon River.
• 철이 구리보다 강하다 = Iron is stronger than copper.
• 피는 물보다 진하다 = Blood is thicker than water.

• 진수가 진호보다 더 빨라요 = Jinsu is faster than Jinho.
  
• 저보다 형이 더 잘해요 = My older brother does it better than me.
• 빵보다 밥이 더 좋아요 = I like rice more than bread.

Superlatives [제일]

제일 is added before an adjective to make it a superlative.

• 진수가 제일 빠르다 = Jinsu is the fastest
• 치타가 육지 동물중에서 제일 빠르다 = The cheetah is the fastest among the land animals.
• 에베레스트산은 세계에서 제일 높다 = Mt. Everest is the highest mountain in the world.
  
• 피자가 세계에서 제일 맛있는 음식이다 = Pizza is the most delicious food in the world.
• 제일 아름다운 것은 사랑이에요 = The most beautiful thing is love. [formal spoken form] (Nouns - Present, Past)

세계 = world
맛있다 = delicious
맛있는 = delicious [descriptive form] Adjectives - Descriptive
아름다운 = beautiful [descriptive form]
것 = thing