Two Number Systems
One of the first challenges for Korean learners is discovering that the language has two completely separate number systems. The Sino-Korean system (한자어 수 / hanja-eo su) was borrowed from Chinese characters and is used for dates, money, phone numbers, and minutes. The native Korean system (고유어 수 / goyueo su) is the original Korean counting system and is used for hours, counting objects with counters, and expressing age.
Knowing when to use each system is essential. Using the wrong one does not just sound awkward — in some cases, it will not be understood at all.
When in doubt, learn the context each system belongs to. Sino-Korean handles abstract numbers (dates, money, phone numbers, addresses, minutes), while native Korean handles tangible counting (objects, hours, age). Once you memorize which situations use which system, choosing the right one becomes automatic.
Sino-Korean Numbers: 1-10
The Sino-Korean system is built from Chinese-origin readings and follows a perfectly logical pattern. These numbers form the foundation for counting money, telling dates, giving phone numbers, and much more.
일, 이, 삼, 사, 오
il, i, sam, sa, o
One, two, three, four, five.
육, 칠, 팔, 구, 십
yuk, chil, pal, gu, sip
Six, seven, eight, nine, ten.
Building Larger Sino-Korean Numbers
The system is beautifully regular. Tens are formed by combining a digit with 십(sip), hundreds with 백(baek), thousands with 천(cheon), and ten-thousands with 만(man).
이십삼
i-sip-sam
Twenty-three (2 × 10 + 3).
삼천오백원이에요.
samcheon-obaek-won-ieyo.
It is 3,500 won.
Key units:
- 십 (sip) — 10
- 백 (baek) — 100
- 천 (cheon) — 1,000
- 만 (man) — 10,000
Native Korean Numbers: 1-10
The native Korean system has its own set of words for 1 through 99. These are the numbers used when counting things with counter words, telling the hour, and stating age.
하나, 둘, 셋, 넷, 다섯
hana, dul, set, net, daseot
One, two, three, four, five.
여섯, 일곱, 여덟, 아홉, 열
yeoseot, ilgop, yeodeol, ahop, yeol
Six, seven, eight, nine, ten.
Larger native Korean numbers combine tens and units: 열하나 (11), 열둘 (12), 스물 (20), 서른 (30), 마흔 (40), 쉰 (50), 예순 (60), 일흔 (70), 여든 (80), 아흔 (90).
Native Korean numbers only go up to 99. Once you reach 100 and beyond, the Sino-Korean system takes over entirely. So 백 (baek) is always used for 100 — there is no native Korean equivalent.
Shortened Forms Before Counters
When native Korean numbers appear directly before a counter word, certain numbers change to shortened forms. This is mandatory, not optional.
The numbers 하나, 둘, 셋, 넷, and 스물 MUST be shortened to 한, 두, 세, 네, and 스무 when they appear before a counter. Saying "하나 개" instead of "한 개" is a clear grammatical error that will sound very unnatural.
사과 두 개 주세요.
sagwa du gae juseyo.
Please give me two apples.
커피 한 잔 마셨어요.
keopi han jan masyeosseoyo.
I drank one cup of coffee.
The shortened forms are:
- 하나 → 한 (han)
- 둘 → 두 (du)
- 셋 → 세 (se)
- 넷 → 네 (ne)
- 스물 → 스무 (seumu)
When to Use Which System
Sino-Korean Is Used For:
- Minutes: 삼십 분 (samsip bun — 30 minutes)
- Dates: 이월 십팔일 (iwol sip-pal-il — February 18th)
- Phone numbers: 공일공-이삼사오 (gong-il-gong i-sam-sa-o)
- Money: 만 원 (man won — 10,000 won)
- Floors and addresses: 삼 층 (sam cheung — 3rd floor)
- Months: 유월 (yuwol — June)
Native Korean Is Used For:
- Hours: 두 시 (du si — 2 o'clock)
- Counting objects with counters: 세 명 (se myeong — 3 people)
- Age: 스무 살 (seumu sal — 20 years old)
지금 세 시 삼십 분이에요.
jigeum se si samsip bun-ieyo.
It is 3:30 now.
오늘은 이월 십팔일이에요.
oneul-eun iwol sip-pal-il-ieyo.
Today is February 18th.
Notice how telling time uses both systems: native Korean for the hour (세 시) and Sino-Korean for the minutes (삼십 분).
Common Counter Words
Korean uses counter words (also called classifiers) when counting specific types of things. The counter follows the number: [native Korean number] + [counter].
고양이 세 마리가 있어요.
goyangi se mari-ga isseoyo.
There are three cats.
책 다섯 권을 읽었어요.
chaek daseot gwon-eul ilgeosseoyo.
I read five books.
Essential Counters
- 개 (gae) — general objects (the most versatile counter)
- 명 (myeong) — people (polite/formal)
- 사람 (saram) — people (casual)
- 마리 (mari) — animals
- 잔 (jan) — cups and glasses of drinks
- 권 (gwon) — books and volumes
- 장 (jang) — flat things (paper, tickets, photos)
- 병 (byeong) — bottles
- 대 (dae) — vehicles and machines
- 벌 (beol) — sets of clothing
Counting Age
Age in Korean uses native Korean numbers with the counter 살(sal).
저는 스물다섯 살이에요.
jeo-neun seumul-daseot sal-ieyo.
I am 25 years old.
우리 아이는 세 살이에요.
uri ai-neun se sal-ieyo.
Our child is 3 years old.
Korea has traditionally used a unique age-counting system where everyone is 1 year old at birth and gains a year every January 1st. This meant Koreans were often 1-2 years "older" than their international age. In 2023, South Korea officially adopted the international age system for legal and administrative purposes, but many Koreans still reference their "Korean age" (한국 나이) in casual conversation.
Quick Reference Table
| Number | Sino-Korean | Native Korean | Shortened Form |
|---|---|---|---|
| 1 | 일 (il) | 하나 (hana) | 한 (han) |
| 2 | 이 (i) | 둘 (dul) | 두 (du) |
| 3 | 삼 (sam) | 셋 (set) | 세 (se) |
| 4 | 사 (sa) | 넷 (net) | 네 (ne) |
| 5 | 오 (o) | 다섯 (daseot) | — |
| 6 | 육 (yuk) | 여섯 (yeoseot) | — |
| 7 | 칠 (chil) | 일곱 (ilgop) | — |
| 8 | 팔 (pal) | 여덟 (yeodeol) | — |
| 9 | 구 (gu) | 아홉 (ahop) | — |
| 10 | 십 (sip) | 열 (yeol) | — |
| 20 | 이십 (isip) | 스물 (seumul) | 스무 (seumu) |
Summary
Korean numbers require learning two parallel systems, but each has a clear domain of use. The key takeaways:
- Learn both systems — Sino-Korean for dates, money, minutes, and phone numbers; native Korean for hours, counting objects, and age
- Master the shortened forms — 한, 두, 세, 네, 스무 are required before counters and are used constantly
- Native Korean numbers cap at 99 — from 100 onward, Sino-Korean is the only system used
- Time uses both systems — native Korean for hours, Sino-Korean for minutes
- Learn common counters — 개 (objects), 명 (people), 마리 (animals), and 잔 (cups) cover the majority of everyday counting needs