When first creating vowel letters, the shapes of ·, ㅡ, and ㅣ were used as the basis.
ㆍ imitates the round shape of the sky, ㅡ imitates the flat shape of the earth,
and ㅣ imitates the shape of a person standing upright.
This is an application of Eastern philosophy that considers the fundamental elements of all things to be heaven, earth, and people.
By combining these three letters, 10 basic vowel letters were created.