Quick answer
Korean has two number systems: Sino-Korean (일, 이, 삼 …) borrowed from Chinese, and native Korean (하나, 둘, 셋 …). The rule that saves the most confusion: Sino-Korean for dates, money, minutes, phone numbers and most counting past 99; native Korean for counting small numbers of objects, telling the hour, and age. Counters (개, 명, 권, 잔 …) sit between the number and the noun.
Two Number Systems
Both systems are used daily — you cannot pick one and ignore the other. The good news is each has a clear domain.
Sino-Korean builds by multiplication and addition: 십 is 10, 이십 is 20, 이십삼 is 23. Native Korean counts up to 99 in practice (십, 스물…), but most daily counting past 99 switches to Sino-Korean. [VERIFY]
When to Use Which
The shortcut
Time splits the two systems: the hour is native (세 시 = 3 o'clock), the minutes are Sino (십오 분 = 15 minutes). Age is native (스물한 살 = 21 years old). Money, dates, and phone numbers are Sino.
Counters
Korean does not say "three books" with the number directly on the noun. It uses a counter — a word that classifies what you are counting — between the number and the noun: 책 세 권 (book three counter-for-bound-objects). The number takes native Korean for counting objects.
Note the special forms: native 하나/둘/셋 shorten to 한/두/세 before a counter (한 개, 두 개, 세 개), and 스물 shortens to 스무 (스무 살). [VERIFY]
Telling Time
Time is the classic mixed case — native for the hour, Sino for the minutes.
For duration, use 시간 (sigan, hours) and 분 (bun, minutes) — both with Sino-Korean: 두 시간 (two hours), 삼십 분 (thirty minutes).
Money, Dates and Age
Money
Dates
Age
Numbers in TOPIK
Numbers and counters appear from TOPIK I (listening questions about time, price, quantity) and stay relevant through TOPIK II, where reading and listening include dates, statistics, and money. Getting the system right also matters in writing — using native for minutes or Sino for age is a clear error. [VERIFY]
Common Mistakes
Avoid these
- Using Sino for age. Age uses native Korean (살).
- Using native for minutes. Minutes use Sino (분); only the hour is native.
- Forgetting the counter. "세 책" is wrong; it is 책 세 권.
- Missing the shortened forms. 하나 개 → 한 개; 셋 시 → 세 시; 스물 살 → 스무 살.
- Mixing systems in one time phrase. Hour = native, minutes = Sino, every time.
- Using native past 99. Most counting above 99 switches to Sino-Korean.
Key Takeaways
Remember these
- Two systems: Sino (일, 이, 삼) and native (하나, 둘, 셋).
- Sino for dates, money, minutes, phone numbers, 100+. Native for the hour, age, and counting 1–99 objects.
- Always use a counter for objects: 개 (generic), 명 (people), 권 (books), 잔 (cups), 장 (flat things).
- Time splits: native hour + Sino minutes (세 시 십오 분).
- Learn the shortened forms: 한/두/세/네 before counters, 스무 before 살.
Frequently Asked Questions
Why does Korean have two number systems?
Korean inherited Sino-Korean numbers from Chinese (used for dates, money, and large counts) alongside its native system (used for small counts, hours, and age). Both are fully alive in daily Korean, so learners need both.
Which system do I use for telling time?
Both. The hour uses native Korean (세 시 = 3 o'clock); the minutes use Sino (십오 분 = 15). So 3:15 is 세 시 십오 분.
How do counters work?
You put a counter between the number and what you are counting: [noun] [number] [counter]. 사과 세 개 = apple three (counter) = three apples. The number is usually native Korean for counting objects.
Do numbers change form before counters?
Yes. Native 하나/둘/셋/넷 shorten to 한/두/세/네 before a counter (한 개, 두 권, 세 잔). 스물 shortens to 스무 (스무 살). Sino-Korean numbers do not change.
Which numbers do I use for money and dates?
Sino-Korean for both: 오천 원 (5,000 won), 이천이십육 년 (2026). Age is the exception — it uses native Korean (스물한 살). [VERIFY]