In the Sanskrit script of ancient India, a (a) is the sound of a wide-open mouth with no obstruction, and m (hūṃ, 吽) is the sound of a completely closed mouth. The arrangement of the letter in the Siddhi script begins with a (a) with the mouth wide open and ends with m (hūṃ, 吽) with the mouth completely closed, and from this, “a-un” was considered to represent the beginning to the end of the universe. In addition to the universe, a (a) is sometimes compared to truth and seeking, and m (hūṃ, ūn) to wisdom and nirvana.
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