Connecting Expressions for Reason and Purpose and Predicate Conjugation Expressions

'-고 있다' Progressive Expression

'-고 있다' (-ing, in progress) is attached to a verb stem to show that an action is in progress at the moment of speaking. It is attached to verb stems regardless of whether the stem has a final consonant (batchim), and it is not used with adjectives. Example: 아이가 마당에서 공을 차고 있다. To describe the action of someone who should be honored, change it to '-고 계시다' (honorific progressive). To show an action that was in progress in the past, use '-고 있었다' (was/were -ing).

When matching a sentence to a picture, check the subject, verb, object, and place in order. Even with the same verb, the sentence may not match the picture if the object changes. '읽다' (to read) is a verb that takes as its object something with written text, such as a book or newspaper. Example: 학생이 도서실에서 잡지를 읽고 있다. '치다' (to play, to strike) is a verb that takes as its object an instrument whose keys or strings are struck or plucked, such as a piano or guitar. Example: 누나가 거실에서 기타를 치고 있다.

A noun that indicates a place is where the action happens, so if the verb changes even at the same place, the sentence becomes incorrect. Receiving food at a cafeteria and making food at a cafeteria use different verbs, so they must be distinguished. The action of taking a food tray and receiving food at the serving counter is expressed with '받다' (to receive).

Nouns that express actions, such as '공부' (study), '체조' (exercise), and '청소' (cleaning), are combined with '하다' (to do) to form '공부를 하다', '체조를 하다', and '청소를 하다'. At the library, one opens a book and studies (공부를 하다), and at the park, one raises the arms upward and exercises (체조를 하다). One may also clean the street by sweeping it with a broom (청소를 하다).

Words for places that seem similar, such as river, sea, and mountain, must also be distinguished. A road along a river is called '강변' (riverside), and the image of riding a bicycle forward along the riverside is expressed as '자전거를 타고 있다' (is riding a bicycle). At an art museum or exhibition hall, the action of looking at hung works is appropriate, and at a photo studio, the action of taking pictures is appropriate.

Jobs and work places should also be remembered together with their verbs. At a factory, '조립하다' (to assemble) is used for fitting parts together to make a finished product, and at a gas station, '넣다' (to put in, to fill) is used for putting fuel into a car. Filling fuel at a gas station is also expressed with '넣다' in the same way. Interior work that repairs and decorates walls and ceilings is called '인테리어 공사' (interior renovation work), and it is distinguished from foundation work, which digs into the ground. Washing windows by hanging from a rope on the outer wall of a building is different from '불을 끄다' (to put out a fire), which is a firefighting activity.

'올라가다' (to go up) is a verb that describes movement from below to above, so it is used for stairs or hills. The action of stepping up the stairs one step at a time is expressed well with '올라가다'.

Tools and means are expressed with '(으)로' (by means of, with). After a vowel or a final consonant ㄹ, '로' is used, and after other final consonants, '으로' is used. It is used as in 휴대전화로 사진을 찍다 (to take a picture with a mobile phone) and 행주로 식탁을 닦다 (to wipe the table with a dish towel), so the combination of the tool and the verb must be checked.

Verbs for washing or wiping also change depending on the object. Clothes are expressed with '빨다' (to wash), hair with '감다' (to wash), and teeth with '닦다' (to brush). The action of rubbing the surface of a dish with a sponge and detergent is also expressed with '닦다'. Washing dishes as a household chore is expressed as '설거지를 하다' (to do the dishes), and it is distinguished from laundry. The work of pushing snow to one side to remove it is '눈을 치우다' (to clear snow), and it must not be confused with planting trees. The action of pushing or pulling an open window back into its place is '닫다' (to close), and it is the opposite of '열다' (to open).

'마시다' (to drink) takes as its object things that can be drunk, such as water, tea, or beverages, and it expresses the action of putting a cup to the mouth and tilting it.

'-면서' (while) expresses that one subject is carrying out two actions at the same time. It is used as in 창밖을 보면서 커피를 마시다 (to drink coffee while looking out the window), and the earlier action and the later action proceed together.

For verbs that express postures, such as '앉다' (to sit), '서다' (to stand), and '눕다' (to lie down), it is natural to use '-아/어 있다' (to be in a state of having done) rather than '-고 있다' to express the state. Examples are 앉아 있다 (is sitting), 서 있다 (is standing), and 누워 있다 (is lying down). The image of people standing in a line and waiting for their turn is expressed as '서서 기다리다' (to stand and wait), and '-아/어서' (while doing, by means of) shows the posture of the action. The image of lying on the floor and reading a book is expressed as '누워서 책을 읽고 있다' (is lying down and reading a book). A posture and an action can be used together, as in 마루에 앉아서 가방을 정리하고 있다 (is sitting on the floor and organizing a bag). A newspaper is a large sheet of paper that is read by unfolding it, so even with the same '보다' (to look at, to read), one should distinguish it from a book and check what is being read in the picture.

'입다' (to wear on the body), '쓰다' (to wear on the head or face), '신다' (to wear on the feet), and '끼다' (to wear on the hands or fingers) combine with '-고 있다' when expressing the state of wearing clothes or items. It is used as in 그는 검은 외투를 입고 있다 (He is wearing a black coat), and it expresses the state of wearing rather than an action.

The actions of a person who should be honored, such as a grandmother or grandfather, are expressed with '-고 계시다' (honorific progressive). It is used as in 할아버지께서 마당에서 화분에 물을 주고 계시다 (Grandfather is watering a flowerpot in the yard).

What one is doing now and what one wants to do in the future must be distinguished. '-고 있다' is used for something currently in progress, and '-고 싶다' (want to) expresses a wish. Saying that one wants to open a restaurant is a plan, so it is not something in progress now.

'-고 있다' Progressive Expression

'-고 있다'(-go itda; progressive ending meaning "is -ing") is attached to a verb stem to show that an action is in progress at the time of speaking. For '읽다'(to read), it becomes '읽고 있다'(is reading), and for '쓰다'(to write), it becomes '쓰고 있다'(is writing). To describe something that was in progress in the past, change it to '-고 있었다'(-go isseotda; was -ing).

The progressive expression is used only with verbs that describe actions. '-고 있다' is not attached to adjectives, so '예쁘고 있다'(yeppeugo itda) is an incorrect expression. To describe a state, use the adjective as it is, as in '예쁘다'(yeppeuda; is pretty). There are also cases such as '모자를 쓰고 있다'(modjareul sseugo itda; is wearing a hat), which express the state of having clothing or an item on one's body.

In picture questions, convert what the person in the picture is doing into the appropriate verb, and then attach '-고 있다'. A figure sitting at a desk and writing corresponds to '공부하다'(gongbuhada; to study), so express it as '공부를 하고 있다'(gongbureul hago itda; is studying).

When choosing the action in a picture, also check the object and the direction. A figure pushing a window closed by hand is '닫다'(datda; to close), so '창문을 닫고 있다'(changmuneul datgo itda; is closing the window) is correct. It is a different action from '걸다'(geolda; to hang), as in hanging something on a wall.

When the situation in a photo involves opposite actions, the meanings of the vocabulary must be distinguished precisely. A figure getting rained on without an umbrella is '비를 맞고 있다'(bireul matgo itda; is getting rained on), while a figure going under an umbrella or the eaves to block the rain is '비를 피하고 있다'(bireul pihago itda; is avoiding the rain).

A scene of people gathered at a bus stop waiting for a vehicle is written as '버스를 기다리고 있다'(beoseureul gidarigo itda; is waiting for the bus). Its actions differ from scenes of riding a bicycle or crossing a crosswalk, so check the place and the action together.

Washing one's face with water corresponds to '세수하다'(sesuhada; to wash one's face), so write '세수를 하고 있다'(sesureul hago itda; is washing one's face). Washing clothes or wiping a mirror involves a different object and action, so these must be distinguished.

'-고 있다' is used only for actions that are in progress now. What one wants to do in the future is expressed with '-고 싶다'(-go sipda; want to). '배우고 있다'(baeugo itda; is learning) means one is currently learning, while '식당을 하고 싶다'(sikdangeul hago sipda; wants to run a restaurant) is a wish for the future, so the two expressions refer to different points in time.

'-아/어서' Reason Expression

'-아/어서' is a connective ending that indicates that the preceding clause is the reason or cause of the result in the following clause. As in '날씨가 추워서 외투를 입었다'(Because the weather was cold, I put on a coat), the cause in the front clause leads to the action or state in the back clause.

The form of '-아/어서' changes depending on the last vowel of the stem. If the last vowel of the stem is 'ㅏ' or 'ㅗ', '-아서' is attached ('잡다 → 잡아서'(to hold → holding), '작다 → 작아서'(small → being small)). With any other vowel, '-어서' is attached ('젖다 → 젖어서'(to get wet → getting wet), '열다 → 열어서'(to open → opening), '널다 → 널어서'(to hang out → hanging out)). '하다' is written as '해서', contracted from '하여서' ('일을 많이 해서'(because I did a lot of work), '조용해서'(because it was quiet)), and '오다' is written as '와서' ('가져와서'(after bringing)).

Verbs ending in '-리다' change the vowel of the last syllable of the stem to 'ㅕ', so it becomes '-려서'. '잃어버리다' is correctly written as '잃어버려서'.

Irregular conjugations must also be distinguished. '덥다' is an ㅂ irregular verb, so 'ㅂ' changes to '워' via '우', becoming '더워서'(because it is hot). '나르다' is a 르 irregular verb, so it becomes '날라서'(having carried). Conjugating them as regular verbs, such as '덥어서' or '나르어서', is wrong.

'열다' and '널다' are regular verbs, so they are written as '열어요' and '널어요'. Omitting '-어' as in '열요', or adding '-여' as in '널여요', gives incorrect forms.

Do not attach the past tense marker '-었-' to the clause before '-아/어서'. Writing '비가 왔어서' is wrong, and '잃었어서' must also be corrected to '잃어서'.

'끝나다' is used with '-니까' as in '끝나니까', and '끝으니까' is an incorrectly conjugated form. Also, motion verbs such as '가다' attach '에' to the destination, as in '출입국사무소에 갔다'(went to the immigration office).

In fill-in-the-blank questions, choose the vocabulary that fits as the cause. '젖다' means damp with moisture on it, and '건조하다' means dry without moisture, so the two are opposites. A situation that is slippery due to moisture is expressed as '젖어서'.

'아프다' means having an illness or pain in the body, so it becomes the reason for going to a hospital. '고프다' means the stomach is empty, '친하다' means the relationship is close, and '걷다' means moving the feet to travel, so none of them fit a context describing the state of the body.

'다치다' means to get an injury on the body, and '걸리다' means to catch an illness. '잡다' means to grip with the hand, and '들다' means to lift an object upward, so '다쳐서'(because one got hurt) fits the context of being hospitalized after injuring a hand.

'벌다' means to earn money by working. '잃다' means to lose what one had, '팔다' means to exchange an item for money, and '버리다' means to discard something as useless. Therefore '벌어서'(having earned) fits the context of saving money to buy a big house.

A poor condition of the eyes is expressed as '나쁘다', which becomes the reason for needing glasses. '못하다' means lacking ability, '싫다' means not liking, and '작다' means small in amount, so none of them can describe the condition of the eyes.

An object too heavy to lift alone is expressed as '무겁다'. '가볍다' means light in weight, so it is the opposite. '가깝다' refers to distance, and '어렵다' means not easy, so neither fits a context about weight.

The reason for crying while watching a drama is '슬프다'(sad). '기쁘다', '신나다', and '좋다' express pleasant or satisfying emotions, so they are not reasons for crying.

If a sound is small, it is hard to hear, so '작다' expresses the volume of a sound. In a situation where one asks someone to speak louder because it is hard to hear, '작아서'(being quiet) fits. '크다' has the opposite meaning, so it does not fit this context.

'끝내다' means to finish work. A situation where today's work could not be completed and more must be done fits '끝내서'(having finished). '받다', '시작하다', and '만들다' do not match the meaning of finishing work.

The meaning of being careful not to fall on a slippery road is '조심하다'(to be careful). '전화하다', '연락하다', and '출발하다' do not match the meaning of being careful in a walking situation.

'-아/어서' is also used when stating emotions or states as reasons. A smiling appearance caused by being in a good mood is written as '기분이 좋아서 웃고 있다'(smiling because one is in a good mood). '기쁘다' expresses happiness, and '신나다' expresses excitement.

When traffic is blocked because there are many cars, '밀리다' is used. A situation where cars are lined up and jammed, making traffic congested, is expressed as '차가 밀려서'(because traffic is backed up).

For questions asking '왜'(why), it is natural to answer the cause with a '-아/어서' clause. If asked why one was late, state the cause with '-아/어서', as in '길을 잘못 들어서 늦었다'(I was late because I took the wrong road).

In reading comprehension problems that ask for a reason in a text, the clause with '-아/어서' gives the reason. If asked why someone is tired, look for the '-아/어서' clause that states the cause, and distinguish tasks to do or time information from the cause.

'-아/어서' and '-(으)니까' can often be used interchangeably, but if a command or suggestion follows, '-아/어서' is not used. '피곤해서 먼저 쉬세요' sounds unnatural, so '-(으)니까' is used instead, as in '피곤하니까 먼저 쉬세요'(Since you are tired, please rest first).

Past Tense '-았/었-'

-았/었- is a past tense ending that indicates an action that took place before the time of speaking. If the last vowel of the verb stem is 'ㅏ' or 'ㅗ', attach '-았-'; for any other vowel, attach '-었-'. For example, '받다' becomes '받았다' and '먹다' becomes '먹었다'.

Verbs ending in '-하다' become past forms by changing '하' to '했'. '청소하다' becomes '청소했다', and '연장하다' also becomes '연장했다'. Words formed by adding '하다' to a noun follow the same pattern and become '했다'. For example, '정하다' becomes '정했다'.

When a verb stem combines with '-았/었-', two syllables are often contracted. '가다' becomes '갔다', '사다' becomes '샀다', and '끼다' becomes '꼈다'; '꼈다', the contracted form of '끼었다', is the standard form. Writing '가았다' or '사았다' without contraction is an incorrect spelling.

The verbs '쓰다' and '끄다' lose the vowel 'ㅡ' from their stems and combine with '-었-'. Therefore their past forms are '썼다' and '껐다', and '쓰어요' and '끄어요' are incorrect spellings. The present forms are written as '써요' and '꺼요'.

Irregular conjugations also apply to past forms. '걷다', an 'ㄷ' irregular verb, becomes '걸었다'; '낫다', an 'ㅅ' irregular verb, is written as '나았다'; and '아프다' is written as '아팠다'. The past form of '기다리다' is '기다렸다', and '기달렸다' is an incorrect spelling.

'만들다' is written as '만들었다' without dropping the 'ㄹ'. '만드렸다' and '만드어요' are incorrect spellings.

Adjectives also express the past tense with '-았/었-'. '어렵다' is an 'ㅂ' irregular adjective, so it becomes '어려웠다'; it is used when contrasting the earlier state with the current state. For example, the weather was hot at first.

The past form of '되다' is '됐다', and before '-어서' it becomes '돼서'. '되서' is not a standard spelling.

The past form of '짜다' is '짰다', and the past form of '캐다' is '캤다'. The vowel 'ㅏ' of the stem and '-았-' merge into contracted forms such as '짰' and '캤'. For example, she dug up sweet potatoes from the ground.

When a word indicating a past time, such as '어제' or '지난주', is present, the predicate must also be in the past tense. Using '-ㄹ 거다', which expresses the future, makes the tense inconsistent. For example, I rode the subway yesterday.

In a text that describes past events in order, determine which action has already occurred by the '-았/었-' in the predicates. Check the sequence of the two events together with time expressions such as '후에' and '전에'.

Questions about what someone did in the past also use '-았/었-'. For example, what did you buy last weekend?

Taking a photograph is expressed with '찍다', and drawing a picture is expressed with '그리다'. For example, he drew a picture. Using '하다' with a picture or photograph sounds unnatural.

The following are commonly confused pairs and their differences.

• 월급을 받다 — means to receive money or allowance. Since an allowance is not something one eats, '수당을 먹다' sounds unnatural. Ex) 지난달에 월급을 받았다.
• 쓰다 / 씻다 — writing characters on a contract is '쓰다', while '씻다' means to wash the body or an object with water. Ex) 손을 씻었다.
• 타다 / 내리다 / 막히다 — '타다' becomes '타면', and '타으면' is an incorrect spelling. '내리다' conjugates as '내려서' and '막히다' as '막혀서'; '내리서' and '막히서' are wrong. Ex) 역에서 내려서 걸었다.
• 잃다 / 잊다 — losing an object is '잃어버리다', while losing memory is '잊어버리다'. Ex) 가방을 잃어버렸다.
• 넣다 / 들어가다 — when moving a thing or animal to another place, use '넣다'. Ex) 상자에 물건을 넣었다.
• 주시다 — the honorific form of '주다'. When the subject to be honored is the subject of the sentence, insert '-시-' and write '주셨다'.

'-(으)려고' Purpose Expression

'-(으)려고' is a connective ending attached to verb stems to express the purpose or intention of an action that one is about to perform. It is written as '-려고' after a stem without a final consonant and as '-으려고' after a stem with a final consonant. A stem ending in 'ㄹ' takes '-려고', as if it had no final consonant. For example, 고향에 선물을 보내려고 우체국에 갔다. (I went to the post office to send a gift to my hometown.)

'-(으)려고' cannot be followed by a command or suggestion in the following clause, and it is not attached to adjectives. '크려고'(incorrect form) is an incorrect expression.

It must be distinguished from '-아/어서'. '-아/어서' expresses a reason, in which the preceding fact causes the following event, while '-(으)려고' expresses the intention to carry out the following action. For example, 비가 와서 집에 있었다. (I stayed home because it was raining.) expresses a reason, while 우산을 사려고 가게에 갔다. (I went to the store to buy an umbrella.) expresses a purpose.

'-(으)러' is used with movement verbs such as '가다'(to go), '오다'(to come), and '다니다'(to commute) to express purpose. For example, 돈을 찾으러 은행에 갔다. (I went to the bank to withdraw money.)

'-(으)려고 하다' is used to talk about a plan or intention that has not yet been carried out. For example, 주말에 친구를 만나려고 한다. (I plan to meet a friend on the weekend.)

The following words are often used in purpose expressions.

• 부치다 — means to send a letter or an item by mail. '붙이다' means to make one thing stick to another, so it is not used to mean mailing. Ex) 고향에 소포를 부치려고 우체국에 갔다. (I went to the post office to send a package to my hometown.)
• 취직하다 — means to get a job at a company. Ex) 좋은 회사에 취직하려고 한국어를 배운다. (I study Korean to get a job at a good company.)
• 연장하다 — means to extend a period of time. Ex) 계약 기간을 연장하려고 회사와 다시 상의했다. (I consulted the company again to extend the contract period.)
• 다녀오다 — means to go to a place and come back. Ex) 고향에 잠깐 다녀오려고 기차표를 샀다. (I bought a train ticket to make a short trip back to my hometown.)

Forms with '-으려고' attached to stems must also be spelled correctly. '찾다' is written as '찾으려고', and '찾어' must be written as '찾아'. Attaching '-으면' to '만들다' gives '만들면'. '받다' with '-으려고' gives '받으려고', and '받을려고' is not a standard spelling.

'-아/어야 하다' Obligation Expression

'-아/어야 하다' is an obligation expression attached to verb stems to indicate that an action is necessary or must be done. If the last vowel of the stem is 'ㅏ' or 'ㅗ', '-아야 하다' is used; with any other vowel, '-어야 하다' is used. Therefore '가다' becomes '가야 하다', and '신다' becomes '신어야 하다'.

A word formed with '하다' is written as '해야', the contracted form of '하여야'. For example, '출근하다' becomes '출근해야 하다', so '퇴근하야' is an incorrect form.

When a stem ends in 'ㅐ' or 'ㅔ', '-어야' is shortened to '-야'. '매다' becomes '매야', the contracted form of '매어야'. '쓰다' loses its '一' vowel and becomes '써야', so '쓰어야'(incorrect form) is an incorrect form. '치우다', which ends in '우', is also conjugated as '치워야'.

In questions about obligation expressions, you must know the meaning of the vocabulary as well as the conjugated forms in order to choose the answer. '출근하다' means to go to the company to do one's work, so when one must be at the company by a set time, one says 출근해야 합니다. (I have to go to work.) '퇴근하다' means to finish work and go home, so it must be distinguished from 출근.

'치우다' means to remove something dirty or messy. Things that are not clean, such as trash or dust, are described with '치워야', and it must be distinguished from words with different meanings, such as '쓰다' and '놓다'. '쓰다' means to place something such as a hat or a safety helmet on the head, so '써야' is used for items that protect the head.

The obligation expression must be distinguished from the prohibition expression. A prohibition is expressed with '-지 마세요', as in 들어가지 마세요. (Do not go in.), and attaching 마세요 to '-아/어', as in 들어가 마세요, is an incorrect form.

'-(으)세요' Request Expression

'-(으)세요' is attached to verb stems to ask or recommend that the listener do an action. It is written as '-세요' after a stem without a final consonant and as '-으세요' after a stem with a final consonant. For example, '쓰다' becomes '쓰세요', and '읽다' becomes '읽으세요'.

A verb ending in 'ㄹ' drops the 'ㄹ' when combined with '-세요'. '들다' becomes '드세요', and '살다' becomes '사세요'. Keeping the 'ㄹ' and attaching '-러요', as in '드러요'(incorrect form), is an incorrect form.

'-(으)세요' is often used in notices and instructions that tell the reader what to do, in order. Expressions that direct a movement, such as 팔을 머리 위로 올리세요. (Raise your arms above your head.), are linked to questions that ask who actually performs that movement. In texts that recommend several actions, you must distinguish between the actions mentioned in the text and those not mentioned.

'-(으)세요' is used to recommend doing an action, so a prohibition against doing something is expressed with '-지 마세요'. You must distinguish this point.

'-아/어 보세요' expresses a suggestion to try something once. It is used as in 메뉴판을 읽어 보세요. (Try reading the menu.), where the verb '읽다' is conjugated as '읽어'.

'입다', '쓰다', '신다', and '벗다' are used differently depending on the body part being worn. '입다' means to put clothes on the body, and '쓰다' means to place a hat or glasses on the head or face. '신다' means to put shoes or socks on the feet, and '벗다' means to take off what one has been wearing. When it is cold, one says 추울 때는 옷을 입으세요. (When it is cold, put on your clothes.)

'가져가다' means to carry an item and take it to another place. When the weather is cloudy, you can recommend that someone take something along, as in 날이 흐릴 때 지갑을 가져가세요. (When the weather is cloudy, take your wallet with you.) '준비하다' means to prepare what is needed in advance, so it is used as in 여행 전에 짐을 준비하세요. (Prepare your luggage before the trip.)

Adjectives of State and Appearance

Adjectives of state and appearance describe the state, shape, size, thickness, temperature, brightness, and other qualities of things or people. In questions that ask you to choose the right sentence for a picture or photo, you need to find the adjective that accurately describes the features shown in the picture. Learning opposite words in pairs can reduce confusion.

• 뜨겁다 — It means high in temperature. It is used for steaming soup or food. Ex) 국이 뜨거우니까 식혀서 드세요. (The soup is hot, so please let it cool before eating.)
• 시원하다 — It means the temperature is low enough to feel pleasant. It is used for water you drink when you are hot. Ex) 바람이 시원해서 좋아요. (The breeze is refreshing, so it feels nice.)
• 미끄럽다 — It describes a state in which the feet do not grip and slide easily. It is used for wet floors and is said like Ex) 비가 와서 계단이 미끄러우니 조심하세요. (It rained, so the stairs are slippery, so please be careful.)
• 넓다 / 좁다 — It means that a space or area is large or small. It is used when talking about the size of a space, such as a room or living room. Ex) 교실이 좁아서 불편해요. (The classroom is cramped, so it is inconvenient.)
• 두껍다 / 얇다 — It means that the thickness is great or small. It is used when talking about the thickness of clothes or books, and thick clothes are worn when the weather is cold.
• 가볍다 / 무겁다 — It means that the weight is small or great. It is used for the weight of objects, not for thickness. It is an 'ㅂ' irregular verb, so it is conjugated as '무거워요' (heavy).
• 크다 / 작다 — It means that the size is large or small. When the size of clothes or objects does not fit, you say it is 작다 (small).
• 어둡다 / 밝다 — It means that there is little or much light. If the weather is cloudy, the inside of a building can be dark even during the day.

In picture questions, the key is to pick out the adjective that does not match the facts shown in the picture. If the picture shows water pooled on the floor, '미끄럽다' (slippery) is correct, while an adjective that expresses an evaluation or judgment with no basis in the picture is not correct.

Sound and Noise Adjectives

Sound and noise adjectives describe how loud a sound is or how it sounds to the listener. '시끄럽다' (noisy) is an 'ㅂ' irregular verb, so it is conjugated with the 'ㅂ' of the stem changing to '워', as in '시끄러워요'.