In short

To turn an adjective into an adverb, add -게 to its stem: 조용하다 (to be quiet) -> 조용하게 (joyonghage, quietly). A small memorized set uses -이 or -히 instead (많이 a lot, 빨리 quickly, 열심히 hard). And to say something becomes a certain way, Korean has three tools chosen by word class: a noun takes 이/가 되다 (의사가 되다, become a doctor), a verb takes -게 되다 (가게 되다, end up going), and an adjective takes -아/어지다 (좋아지다, get better).

The rule

Step 1 - Making adverbs with -게 (the productive rule)

Take any 형용사 (adjective) stem and add -게. Unlike most endings, -게 has no allomorph - it attaches straight to the stem whether or not there is a 받침, and irregular stems do not change before it:

Adjective stem + -게 -> 크다 (to be big) -> 크게 (keuge, loudly, in a big way), 쉽다 (to be easy) -> 쉽게 (swipge, easily), 맛있다 (to be tasty) -> 맛있게 (masitge, deliciously), 늦다 (to be late) -> 늦게 (neutge, late). Even 그렇다 (to be so) gives the everyday adverb 그렇게 (geureoke, like that). This is the safe, always-available way to build an adverb.

Step 2 - The fixed -이 / -히 adverbs

A closed, memorized set of common adverbs is written with -이 or -히 instead of -게: 많이 (mani, a lot, from 많다), 같이 (gachi, together, from 같다), 빨리 (ppalli, quickly, from 빠르다), 천천히 (cheoncheonhi, slowly), 조용히 (joyonghi, quietly), 깨끗이 (kkaekkeusi, cleanly), 열심히 (yeolsimhi, diligently). Separately, a few everyday adverbs are not built from an adjective at all and are simply learned as words: 일찍 (iljjik, early), 잘 (jal, well). Some adjectives allow both, with the same meaning: 조용하다 -> 조용하게 = 조용히 (quietly). Whether a word takes -이 or -히 is a spelling fact to memorize (see lesson 46); when unsure, the -게 form in Step 1 is almost always acceptable.

Step 3 - Degree adverbs

These sit before the verb, adjective or adverb they scale: 아주 (aju, very), 너무 (neomu, too / really), 정말 (jeongmal, really), 조금 (jogeum, a little), 별로 (byeollo, not really - requires a following negative), 훨씬 (hwolssin, much, by far - usual with 더 in a comparison, but it does not need one). So 아주 좋아요 (very good), 아주 조용하게 (very quietly), 조금 빨리 (a little faster), 별로 안 좋아요 (not that good), 훨씬 더 좋아요 (much better), 훨씬 좋아졌어요 (has got a lot better).

Step 4 - Change of state: three ways to say “become”

Which “become” you use depends on the word class of what precedes it:

• Noun + 이/가 되다 - become that thing. Use the subject particle 이/가, never 을/를: 의사 -> 의사가 되다 (uisaga doeda, become a doctor), 봄 -> 봄이 되다 (bomi doeda, spring comes). 되다 conjugates 되 + 어요 -> 돼요 / past 됐어요 (dwaesseoyo).
• Verb stem + -게 되다 - come to / end up doing, usually as the result of circumstances beyond your control: 하다 -> 하게 되다, 가다 -> 가게 되다 (gage doeda, end up going), 알다 -> 알게 되다 (alge doeda, come to know). 그렇게 하게 됐어요 (geureoke hage dwaesseoyo, that’s how it ended up) frames the outcome as not fully your choice.
• Adjective + -아/어지다 - gradually become that quality. Built on the 아/어 form, so irregular stems show their irregularity: 좋다 -> 좋아지다 (joajida, get better), 춥다 -> 추워지다 (chuwojida, get cold), 비싸다 -> 비싸지다 (bissajida, get expensive), 예쁘다 -> 예뻐지다 (yeppeojida, get prettier), 많다 -> 많아지다 (manajida, increase). It is written as one word, with no space.

Scope note: attaching -아/어지다 to a transitive verb (만들어지다 get made, 정해지다 get decided) forms a passive - that belongs to lesson 55. Here -아/어지다 is only the change-of-state ending on adjectives.

Forms & patterns

Building adverbs:

The three “become” patterns:

Examples

Common mistakes

• 의사를 됐어요. (Uisareul dwaesseoyo.) -> 의사가 됐어요. (Uisaga dwaesseoyo.) - “become N” takes the subject particle 이/가, never the object particle 을/를.
• 날씨가 추워 됐어요. (Nalssiga chuwo dwaesseoyo.) -> 날씨가 추워졌어요. (Nalssiga chuwojeosseoyo.) - an adjective “becomes” with -아/어지다; you do not put 되다 after the 아/어 form.
• 공부를 많게 했어요. (Gongbureul manke haesseoyo.) -> 공부를 많이 했어요. (Gongbureul mani haesseoyo.) - the adverb of 많다 is the fixed 많이. (많게 is a possible form of 많다, but it does not mean a lot modifying a verb like this.)
• 별로 비싸요. (Byeollo bissayo.) -> 별로 안 비싸요. (Byeollo an bissayo.) - 별로 must be paired with a negative (안 / -지 않다).
• 한국에서 일하게 되요. (Hangugeseo ilhage doeyo.) -> 한국에서 일하게 돼요. (Hangugeseo ilhage dwaeyo.) - 되 + -어요 contracts to 돼요, never *되요.

Tips

• -게 is your usual fallback. From most adjectives, stem + -게 gives a working adverb, often equal to the -이/-히 form where one exists (조용하게 = 조용히). The short -이/-히 adverbs (많이, 빨리, 열심히) are a closed set worth memorizing outright - and for the commonest ones the -게 form is no substitute: a lot is always 많이, never 많게.
• Match the “become” to the word class. A NOUN -> 이/가 되다 (의사가 되다); a VERB you end up doing -> -게 되다 (가게 되다); an ADJECTIVE quality that shifts -> -아/어지다 (좋아지다). Line up the trigger with the part of speech and you will pick the right one.
• -게 되다 softens agency. 안 가요 = “I’m not going (my choice)”; 못 가게 됐어요 = “it turned out I can’t go.” Because circumstances - not you - decided, -게 되다 is a polite, face-saving way to decline or explain.
• -아/어지다 rides the 아/어 form, so all the irregulars carry over: 춥다 -> 추워지다, 예쁘다 -> 예뻐지다, 낫다 -> 나아지다. If you can build the 해요체 form, you can build the change-of-state form.