There are actually 2 number systems that are used: The Pure Numbers and Sino-Korean numbers which are borrowed actually from chinese counting system. Pure Korean: 1 - Hana - 하나 2 - Duhl - 둘 3 - Set - 셋 ('T' is semi-silent) 4 - Net - 넷 ('T' is semi-silent) 5 - Daseot - 다섯 ('T' is semi-silent) 6 - Yeoseot - 여섯 ('T' is semi-silent) 7 - Ilgop - 일곱 8 - Yeodeol 여덟 9 - Ahop - 아홉 10 - Yeol - 열 Sino-Korean: 1 = il/일 2 = ee/이 3 = sam/삼 4 = sa/사 5 = oh/오 6 = yuk/육 7 = chil/칠 8 = pal/팔 9 = goo/구 10 = ship/십 When to use which depends on the context of the sentence.