Hunminjeongeum · Sejong's Preface

ㅓ ㅑ ㅕ (i a eo ya yeo), human vowel sounds, are placed
    to the right of the initial sounds.


    Three phoneme structure: Initial, Medial, Final
    Every syllable is composed of three phonemes(CVC):
    initial Consonants, medial Vowels, initial Consonants.
    These phonemes combine to form a complete syllable.


    Tones
    If you add one dot (ㆍ) to the left of a syllable block, it
    means the high tone. If you add two dots (:) to the left, it
    becomes a rising tone. If there are no dots, it is a low, flat
    tone .
    For an abrupt falling tone, the dots are used in the same
    way, but the sound is very short and quick.




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