A foreign student looked at the clock and asked. "Teacher, why do you say '두 시 삼십 분' instead of '이 시 삼십 분'?" I've spoken that way all my life, but I had never thought about the reason. ## The numbers came down in two lines Korean has two sets of numbers. 하나, 둘, 셋 are native Korean words (고유어) that have been used since long ago. 일, 이, 삼 are words (Sino-Korean words) that came from China along with Chinese characters. Because the two sets have lived side by side for so long, each word has settled on the one that suits it. ## 시 takes native Korean words, 분 takes Sino-Korean words Before "시," we use native Korean numbers. It's 한 시, 두 시, 세 시. Before "분," we use Sino-Korean numbers. Ten minutes, thirty minutes. So two sets get mixed in a single sentence. Even scholars can't give one single answer as to why they split. Still, many people think the hour comes closer to words people have long used when counting "one, two," while dividing time into minutes was an idea that arrived along with clocks, which is why Sino-Korean words were attached. ## Remember it like this Native Korean numbers are usually only used up to "아흔아홉" (ninety-nine). So we use Sino-Korean numbers for big numbers, dates, phone numbers, and money. Like 이천 원 (2,000 won) and 삼월 오 일 (March 5). When counting people or things, we use native Korean numbers. Age works the same way: we say "스물다섯 살" (25 years old). There's one rule you can start using right away. **Use native Korean numbers before "시", "살", "개", and "명", and Sino-Korean numbers before "분", "원", "월", and "일".** Even if it's not perfect, people will understand you most of the time.