Why Korean particles have two forms
Many of the most common Korean particles come in two forms, and the choice is purely about sound: one form follows a word that ends in a consonant, the other a word that ends in a vowel. The consonant at the end of a syllable is called 받침 (batchim). 학생 ends in the consonant ㅇ, so it takes 학생은, 학생이, 학생을. 친구 ends in the vowel ㅜ, so it takes 친구는, 친구가, 친구를.
One exception catches almost every learner: (으)로 drops 으 after ㄹ, so it is 서울로 and 연필로, not 서울으로. And because the rule is about sound, numbers and abbreviations follow how they are read: 3 is 삼, so 3을; 2 is 이, so 2를; TV is 티비, so TV를.
Korean particle cheat sheet
The form depends only on the sound the word ends in. Examples use 학생 (ends in a consonant), 친구 (ends in a vowel) and 서울 (ends in ㄹ).
| Particle | After a consonant | After a vowel | After ㄹ |
|---|---|---|---|
| Topic | 은 학생은 | 는 친구는 | 은 서울은 |
| Subject | 이 학생이 | 가 친구가 | 이 서울이 |
| Object | 을 학생을 | 를 친구를 | 을 서울을 |
| And / with | 과 학생과 | 와 친구와 | 과 서울과 |
| To / by means of | 으로 학생으로 | 로 친구로 | 로 서울로 |
| Is (polite) | 이에요 학생이에요 | 예요 친구예요 | 이에요 서울이에요 |
| And / with (casual) | 이랑 학생이랑 | 랑 친구랑 | 이랑 서울이랑 |
| Is (casual) | 이야 학생이야 | 야 친구야 | 이야 서울이야 |
| Was (polite) | 이었어요 학생이었어요 | 였어요 친구였어요 | 이었어요 서울이었어요 |
| Called / said | 이라고 학생이라고 | 라고 친구라고 | 이라고 서울이라고 |
| Or / about | 이나 학생이나 | 나 친구나 | 이나 서울이나 |
| Even / at least | 이라도 학생이라도 | 라도 친구라도 | 이라도 서울이라도 |
| Any / either | 이든지 학생이든지 | 든지 친구든지 | 이든지 서울이든지 |
| As (a role) | 으로서 학생으로서 | 로서 친구로서 | 로서 서울로서 |
| By means of (formal) | 으로써 학생으로써 | 로써 친구로써 | 로써 서울로써 |
| Listing | 이며 학생이며 | 며 친구며 | 이며 서울이며 |
| Calling a name | 아 학생아 | 야 친구야 | 아 서울아 |
Common particle mistakes
Topic particle after a consonant
학생는 한국 사람이에요.
학생은 한국 사람이에요.
학생 ends in ㅇ, a consonant, so the topic particle is 은.
Object particle after a vowel
친구을 만났어요.
친구를 만났어요.
친구 ends in a vowel, so the object particle is 를.
(으)로 after ㄹ
서울으로 가요.
서울로 가요.
After ㄹ, (으)로 is always 로: 서울로, 연필로, 지하철로.
나 as the subject
나가 할게요.
내가 할게요.
나, 저 and 너 have their own subject forms: 내가, 제가, 네가.
아니에요, not 아니예요
학생이 아니예요.
학생이 아니에요.
아니다 is not a noun with 이에요: its stem 아니- takes -에요 directly, so it is 아니에요 (shortened: 아녜요), never 아니예요.
예요 after a vowel
저는 의사이에요.
저는 의사예요.
After a word ending in a vowel, standard spelling accepts only the contracted 예요: 의사예요, 친구예요. After a consonant it is 이에요: 학생이에요.
과 / 와
책와 연필
책과 연필
책 ends in ㄱ, so 'and' is 과. After a vowel it is 와: 커피와 빵. In speech, 하고 or (이)랑 is more common.
Numbers follow the reading
3에 2을 더하면 5예요.
3에 2를 더하면 5예요.
In arithmetic 2 is read 이 (Sino-Korean), which ends in a vowel, so 2를. But 3을 (삼) and 1을 (일). Counting objects in native Korean is different: 둘을.
How the chooser works
- The chooser finds the last syllable of the word as it is read aloud. For Hangul, it splits that syllable into its letters using the Unicode structure of Hangul, which is exact: no dictionary is involved.
- Numbers are read in Sino-Korean (3 → 삼, 2,000 → 이천, 3.5 → 삼 점 오), with the native reading (둘, 셋) shown when it gives a different form. Units and currencies are read the way Korean reads them (5kg → 킬로그램, $5 → 5 달러), and abbreviations letter by letter (TV → 티비).
- Then it applies the standard rule: consonant forms after a final consonant, vowel forms after a vowel, and 로 instead of 으로 after ㄹ. 나, 저, 너 and 누구 get their special subject forms (내가, 제가, 네가, 누가). Strictly, 이에요, 이야 and 이었어요 are forms of the copula 이다 (taught in Korea as a predicative particle, 서술격 조사); they follow the same sound rule.
- When the reading could go two ways (MP3: 엠피스리 or 엠피삼), both results are shown. When it can't be known (English words, hanja, fractions like 3/4, times like 10:30), the chooser asks you for the Korean reading instead of guessing.
- Every release is tested on all 11,172 Hangul syllables against Unicode decomposition, on every number from 0 to 100,000 against a separately written number reader, and on about 170 hand-checked words.
The chooser picks the right form of a particle, not which particle your sentence needs: whether 은/는 or 이/가 fits is about meaning and context. It also can't know how you pronounce an English word or an abbreviation read as a word (NASA → 나사), so it asks.
Frequently asked questions
When do I use 은/는 and when 이/가?
This tool picks the right form; which particle to use is about meaning. As a rule of thumb, 은/는 marks the topic or a contrast (저는 학생이에요: as for me, I'm a student), and 이/가 marks the subject, often new information or the answer to 'who?' (누가 왔어요? 민수가 왔어요). To check your actual sentence, use the Korean Grammar Checker.
What is 받침?
받침 (batchim) is the consonant at the bottom of a Hangul syllable block: ㅇ in 생, ㄱ in 책, ㄹ in 울. A word that ends in a syllable with 받침 takes the consonant form of a particle (은, 이, 을); a word without one takes the vowel form (는, 가, 를).
Why is it 서울로 and not 서울으로?
The particle (으)로 adds 으 only after consonants other than ㄹ. After ㄹ it is always 로: 서울로, 연필로, 지하철로. The particles built on it work the same way (서울로서, 칼로써, 서울로부터). The others have no such exception: 서울은, 서울이, 서울을.
Which form do numbers take?
The form follows how the number is read. In Sino-Korean, 2 is 이 (2를), 3 is 삼 (3을), 1 is 일 (1을, 1로), 10 is 십 (10을) and 1,000 is 천 (1,000을). When counting in native Korean the reading changes (2 → 둘 → 2을), and with a counter the counter decides: 3개는, 5명은.
What about English words and brand names?
They follow their Korean pronunciation: Apple is 애플, so Apple을; Google is 구글, so Google을; Netflix is 넷플릭스, so Netflix를. Since the pronunciation can't be worked out reliably from the spelling, the chooser asks you to type it in Hangul.
Is 의사이에요 wrong?
Yes, in standard spelling. After a word ending in a vowel, 이에요 must contract to 예요: 의사예요, 친구예요. After a consonant it stays 이에요: 학생이에요. 아니에요 is a different case: it is never 아니예요.
Why is it 민준이가 and 민준이예요?
When you call someone by their given name alone, a name ending in a consonant takes the suffix 이 before particles: 민준이가, 민준이는, 민준이를, and the National Institute of Korean Language spells 민준이예요, not 민준이에요. Names ending in a vowel don't: 민수가, 민수예요. With the full name or 씨 there is no 이: 김민준이에요, 민준 씨예요.
Is it free? Is my text sent anywhere?
It's free and unlimited, with no sign-up. Everything runs in your browser, so the words you type never leave your device.
Sources
- National Institute of Korean Language: Korean spelling rules (한글 맞춤법)
- National Institute of Korean Language: on 이에요 / 예요 and 아니에요
- National Institute of Korean Language: Basic Korean Dictionary (particle entries)
- Unicode: Hangul Syllables chart (U+AC00–U+D7A3), the structure the chooser decodes
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