Numbers in Korean: Sino-Korean and native counting, 1 to 100 and 억

Why Korean has two sets of numbers

Korean took a large part of its vocabulary from Chinese, read in Korean sound. Numbers came with it: 일 is the Korean reading of 一, 삼 of 三, 만 of 萬. The older Korean words never went away, so the language now keeps two complete ways of saying three, 삼 and 셋, and each has its own territory.

The two halves of the table do not meet in the middle. The native series has words up to 아흔, ninety, and combinations below a hundred such as 아흔아홉, ninety-nine; above that Korean switches to 백, 천 and 만. The Sino-Korean series runs without limit and is the only one used for long figures.

Building larger numbers is regular in both. Sino-Korean multiplies before a unit and adds after it: 이십 is two tens, twenty, and 이십오 is twenty-five. For the teens the 일 is left out, so fifteen is 십오 and not 일십오, as Wikipedia's Korean numerals article notes. The native series simply joins tens and units: 열하나 is eleven, 스물다섯 twenty-five.

Which numbers in Korean go with what

Native numbers count things. With a counter word after them they shorten: one, two, three, four and twenty lose their last sound and become 한, 두, 세, 네 and 스무. 두 개 is two things, 네 명 four people, 스무 마리 twenty animals. The same contraction gives 한 번, once, and 열 번, ten times.

Sino-Korean numbers handle dates, money, minutes, addresses, telephone numbers and anything over ninety-nine. The months on the months in Korean page are all Sino-Korean, as are prices: 만 원 is ten thousand won.

Clock time is the classic trap, because it mixes the two. The hour takes native numbers and the minute Sino-Korean ones: 세 시 is three o'clock, 삼십오 분 thirty-five minutes, so 3:35 is 세 시 삼십오 분.

Age can go either way, and the counter decides. 스물다섯 살 uses the native number with 살; 이십오 세 uses the Sino-Korean number with 세 and sounds more formal. Both mean twenty-five years old.

The counter 번 shows how much the choice of series matters. With a native number it counts occurrences, 열 번, ten times; with a Sino-Korean one it becomes a label, 십 번, number ten.

Counting in ten-thousands: 만 and 억

Large Korean numbers are grouped by four digits, following the Chinese myriad system, where English groups by three. The step after 천, a thousand, is 만, ten thousand, and the next named unit is 억, 10,000 × 10,000, a hundred million. Wikipedia's article adds 조 for 10¹² and notes that units beyond 10²⁰ are rarely used.

Converting means regrouping the digits. A hundred thousand is ten 만, 십만; a million is a hundred 만, 백만; ten million is 천만. Written figures often mix digits and the unit, as in 5,000만 for fifty million.

Zero has two names. 영 is the regular Sino-Korean zero; 공 is an alternative, and Wikipedia's example of it comes from military radio traffic. In phone numbers and similar strings of digits the native words for one and two are sometimes swapped in for 일 and 이, which sound too alike over a bad line.

Sound changes when numbers meet

Spelling stays fixed while pronunciation adapts. Sixteen is written 십육 but pronounced sim-nyuk: the assimilation rules apply as though the underlying form were 십륙, according to the Korean numerals article on Wikipedia. Twenty-six, 이십육, ends the same way.

The months show the opposite case, where spelling gave way to sound: 육 loses its k in 유월, June, and 십 its p in 시월, October. That change is fixed in the orthography and does not spread to other numbers; sixty is still 육십, and article 52 of the Hangul Orthography itself contrasts 시월 with 십일, the tenth day.

Linking also matters. A final consonant moves onto a following vowel, so 십일, eleven, sounds like si-bil; the IPA for 십일월, November, on the months page shows the same link.