한자어 수사 vs 고유어 수사 (Hanja-eo Susa vs Goyueo Susa): Why Korean Has Two Number Systems — and Exactly When to Use Each
You're at a café. The barista asks how many people are in your party. You know the answer is two. But your brain locks up — is it 이 (i) or 둘 (dul)? You've studied both. You know both mean "two." You're stuck anyway.
This isn't a memory problem. It's a logic problem — and the logic has a name.
Korean has two completely separate numeral systems that have coexisted for centuries. Native speakers switch between them without thinking. The switching follows rules — clean, learnable rules. Here's the map.
- • A Tale of Two Number Systems
- • Where Each System Lives: A Practical Map
- • Sino-Korean: The Measured World
- • Native Korean: The Human World
- • The Shape-Shifting Numbers: A Trap That Catches Almost Everyone
- • The Time System: Where Both Numbers Live in One Sentence
- • Age: The One That Surprises Even Intermediate Learners
- • The Zero Nobody Tells You About
- • Apply It Right Now: A 60-Second Checklist
A Tale of Two Number Systems
The native Korean counting words — 하나, 둘, 셋 (hana, dul, set, "one, two, three") — are ancient, woven into the language long before outside influence arrived. Then came centuries of Chinese cultural contact: Confucian texts, administrative systems, formal record-keeping. With it came the Chinese-derived numbers — 일, 이, 삼 (il, i, sam, "one, two, three"). These 한자어 수사 (hanja-eo su-sa, "Sino-Korean numerals derived from Chinese") took root in official and transactional contexts, while the 고유어 수사 (go-yu-eo su-sa, "native Korean numerals, original to the language") kept their hold on everyday human experience.
Both survived. Neither won. And here's the aha moment textbooks quietly skip: the contexts where each system lives aren't random — they map onto a distinction Korean culture has always made between the official world and the human world.
Sino-Korean numbers belong to things that are measured and recorded: money, dates, phone numbers, minutes on a clock. Native Korean numbers belong to things that are encountered and experienced: people in front of you, hours passing, your own age, objects you hold in your hand.
That single distinction will get you right the vast majority of the time — and more importantly, it gives you something to think from instead of two parallel lists you're expected to memorize and hope for the best.
Where Each System Lives: A Practical Map
Sino-Korean: The Measured World
Use 일, 이, 삼 (il, i, sam…) for:
- Dates: 일월 이일 (irwol i-il, "January 2nd")
- Minutes: 삼십 분 (samsip bun, "30 minutes")
- Money: 오천 원 (ocheon won, "5,000 won")
- Phone numbers: 공일공-일이삼사-오육칠팔 (gong-il-gong, il-i-sam-sa, o-yuk-chil-pal)
- School years: 이학년 (i-hangnyeon, "2nd grade")
- Floor numbers: 사층, 오층 (sa-cheung, o-cheung, "4th floor, 5th floor")
- Sequential labels: 삼번 (sam-beon, "number 3")
Native Korean: The Human World
Use 하나, 둘, 셋 (hana, dul, set…) for:
- Hours (o'clock): 두 시 (du si, "2 o'clock"), 열한 시 (yeolhan si, "11 o'clock")
- Age: 스물두 살 (seumuldu sal, "22 years old")
- People: 세 명 (se myeong, "3 people"), 두 분 (du bun, "2 people" — polite form)
- Objects: 한 개 (han gae, "1 item"), 두 개 (du gae, "2 items")
One hard limit: native Korean numbers only go up to 99. 아흔아홉 (aheunaheop, "99") is the ceiling. For 100 and above — 백 (baek, "100"), 천 (cheon, "1,000"), 만 (man, "10,000") — you must use Sino-Korean. There are simply no native Korean words for those quantities. So 백 개 (baek gae, "100 items") and 천 명 (cheon myeong, "1,000 people") are the only options.
The Shape-Shifting Numbers: A Trap That Catches Almost Everyone
Here's something textbooks mention in a footnote and never return to — but it causes constant errors in real conversation.
Korean uses 단위 명사 (dan-wi myeong-sa, "counter words — specific words attached to numbers when counting different categories of things"). Different counters exist for what you're counting: 개 (gae) for general objects, 명 (myeong) for people in neutral contexts, 분 (bun) for people in polite contexts, 마리 (mari) for animals, 권 (gwon) for books, 장 (jang) for flat things like paper or tickets.
When a native Korean number appears directly before any counter, the first four numbers change form:
| Standalone | Before a counter |
|---|---|
| 하나 (hana, "one") | 한 (han) |
| 둘 (dul, "two") | 두 (du) |
| 셋 (set, "three") | 세 (se) |
| 넷 (net, "four") | 네 (ne) |
So you never say 하나 개 — it's 한 개 (han gae, "one item"). Never 둘 명 — it's 두 명 (du myeong, "two people"). The standalone forms (하나, 둘, 셋, 넷) exist only when the number appears alone, without a counter following it. The moment a counter appears, the number shrinks.
This is not optional. 하나 개 sounds immediately wrong to any Korean speaker — though most couldn't explain why. They feel it before they can name it. That's how deep the pattern runs.
The Time System: Where Both Numbers Live in One Sentence
Telling time in Korean is the clearest place to watch both systems work together — and the most reliable place beginners make mistakes.
The rule is elegant:
시 (si, "o'clock") → Native Korean number 분 (bun, "minutes") → Sino-Korean number
So 2:30 is 두 시 삼십 분 (du si samsip bun) — native two, Sino-Korean thirty. One sentence, two systems, zero exceptions.
11:05 is 열한 시 오 분 (yeolhan si o bun) — native eleven, Sino-Korean five.
The most common beginner mistake is saying 이 시 (i si) for "2 o'clock" — Sino-Korean number with the hour counter. Korean speakers will understand you, but it registers as immediately off, the way "I have ate" registers in English: technically parseable, but wrong in a way you feel before you analyze it. The hour always takes a native Korean number. Always. 두 시 (du si) is the only correct form.
You can also say 세 시 반 (se si ban, "3:30") — 반 (ban, "half") is borrowed from Chinese but functions as a natural shortcut for "30 minutes" and is widely used in casual speech.
Age: The One That Surprises Even Intermediate Learners
Age in Korean uses native Korean numbers plus 살 (sal, "years old"):
✅ 스물다섯 살이에요 (seumul-daseo sal-i-eyo, "I'm 25 years old.") ❌ 이십오 살이에요 (isibo sal-i-eyo) — not ungrammatical, but it sounds genuinely strange in conversation, the way reading a birthday card aloud in a robot voice sounds strange. Technically correct, humanly wrong.
Like any language community, Korean speakers vary — regional backgrounds, generations, and personal habits all play a role in how people talk. But the native-number-plus-살 pattern for age is one of the most consistent tendencies in the language, cutting across most contexts and demographics.
A quick note on the age system itself: Korea has traditionally counted age differently from the international standard (born as 1, gaining a year every January 1st rather than on your birthday). Since 2023, official and legal contexts have shifted toward 만 나이 (man na-i, "international age"), so you may encounter 만 스물다섯 살이에요 (man seumul-daseo sal-i-eyo, "I'm 25 in international age") or the formal 만 25세예요 (man isibo se-ye-yo) in official settings. In everyday conversation, both systems still mix — don't be surprised if Koreans give you slightly different answers about their age depending on which system they're using.
The Zero Nobody Tells You About
In formal mathematics, zero is 영 (yeong, "zero — the standard form"). But read a Korean phone number using 영 and you'll get politely confused looks.
In phone numbers, zero is 공 (gong, "zero as used in phone numbers and codes"). Korean mobile numbers typically start with 010, which is read 공일공 (gong-il-gong) — not 영일영. This is one of those small details that immediately signals to any Korean speaker that you've been paying attention to how the language is actually spoken, not just how it appears in textbooks.
Apply It Right Now: A 60-Second Checklist
Next time you reach for a Korean number, run through this:
- Money, date, minutes, phone number, or sequential label? → Sino-Korean: 일, 이, 삼…
- Hours, age, people, or countable objects? → Native Korean: 하나, 둘, 셋…
- Native number going directly before a counter? → Check the form: 하나→한, 둘→두, 셋→세, 넷→네
- Number is 100 or above? → Sino-Korean only. No native Korean equivalent exists.
- Zero in a phone number? → 공 (gong), not 영 (yeong).
Try it now: say your age out loud in Korean. Count the people nearest to you. Read the current time. Three sentences, both systems, the checklist in action. That's not practice for later — that's the lesson landing.
The confusion you've felt around Korean numbers isn't a sign you're bad at this. It's a sign nobody handed you the organizing principle. You have it now. The two systems aren't competing — they're dividing the world between them, and once you see the division, you can't unsee it.
🔊 Pronunciation Guide
Natural-sounding audio for the Korean in this article. Listen, then shadow out loud.
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