However, the tables below are not sufficient for normal transcription of the Korean language as the overarching Revised Romanization of Korean system takes contextual sound changes into account.
Called choseong, or "initials", there are 19 initial consonants, whereof one (ㅇ) is silent, and five (ㄲ, ㄸ, ㅃ, ㅆ, ㅉ) are doubled: Called jungseong, or "vowels", there are 21 medial vowels: Called jongseong, or "finals", there are 27 final consonants; with the additional case of no final consonant, there is a total of 28 possibilities: Several collation sequences are used to order words (like alphabetical sorting).
The North and South differ on (a) the treatment of composite jamo consonants in syllable-leading (choseong) and -trailing (jongseong) position, and (b) on the treatment of composite jamo vowels in syllable-medial (jungseong) position.
This first sequence is official in South Korea (and is the basic binary order of codepoints in Unicode): ㄱ ㄲ ㄴ ㄷ ㄸ ㄹ ㅁ ㅂ ㅃ ㅅ ㅆ ㅇ ㅈ ㅉ ㅊ ㅋ ㅌ ㅍ ㅎ ㅏ ㅐ ㅑ ㅒ ㅓ ㅔ ㅕ ㅖ ㅗ ㅘ ㅙ ㅚ ㅛ ㅜ ㅝ ㅞ ㅟ ㅠ ㅡ ㅢ ㅣ ㄱ ㄲ ㄳ ㄴ ㄵ ㄶ ㄷ ㄹ ㄺ ㄻ ㄼ ㄽ ㄾ ㄿ ㅀ ㅁ ㅂ ㅄ ㅅ ㅆ ㅇ ㅈ ㅊ ㅋ ㅌ ㅍ ㅎ Sequences of this second type are common in North Korea: ㄱ ㄴ ㄷ ㄹ ㅁ ㅂ ㅅ ㅈ ㅊ ㅋ ㅌ ㅍ ㅎ ㄲ ㄸ ㅃ ㅆ ㅉ ㅇ ㅏ ㅑ ㅓ ㅕ ㅗ ㅛ ㅜ ㅠ ㅡ ㅣ ㅐ ㅒ ㅔ ㅖ ㅚ ㅟ ㅢ ㅘ ㅝ ㅙ ㅞ ㄱ ㄳ ㄴ ㄵ ㄶ ㄷ ㄹ ㄺ ㄻ ㄼ ㄽ ㄾ ㄿ ㅀ ㅁ ㅂ ㅄ ㅅ ㅇ ㅈ ㅊ ㅋ ㅌ ㅍ ㅎ ㄲ ㅆ * Consonant names in the 15th century seem to have ended in a vowel (without adding the last consonant repeating a shortened version of the initial), judging from 1451 Hunmin Jeongeum Eonhae's forms such as "ㄱ는", which may have been pronounced geuneun.
To be technical, the silent consonant would be added before the sound (e.g., ㅏ becomes 아).