Numbers one: 일, 이, 삼

These numbers came into Korean with Chinese characters, which is why they are single syllables and sound related to the numbers of Chinese and Japanese. Korean keeps them for anything measured or read as a figure: dates, money, minutes, phone numbers and floors. Tomorrow's native Korean set is for counting objects and people. Which set you use depends on what you are counting, not on how big the number is.

Sino-Korean numbers are arithmetic said aloud: the number of tens, then 십, then the units. 이십오 (isibo) is 'two ten five', 25, and 구십구 (gusipgu) is 'nine ten nine', 99, so once you know one to ten you can say anything up to 999. English hides the pattern behind eleven, twelve and the teens; Korean simply does not have them. The only thing to watch is the sound at the joins, where final consonants link or change exactly as they do inside words.

A phone number is read one digit at a time, and the dash between groups is said as 에 (e), a link between the groups rather than a number. Many Koreans think of that 에 as the possessive marker 의, which is usually pronounced 에 in everyday speech. Zero is 공, from a character meaning empty, rather than 영; the choice is only convention, but it is a firm one. Korean mobile numbers now almost all start 010, so 공일공 is the first thing you hear when someone reads one out.