In the Korean langauge, vowels are divided into 2 groups: ying and yang.
yang vowels: in linguistics, known as ‘low’ vowels – articulated at low positions in the mouth
아, 야, 애, 오, 요, 외, 와, 왜
yin vowels: ‘high vowels’ – articulated at high positions in the mouth
어, 여, 우, 유, 에, 위, 워, 웨, 으, 의, 이
(please note that high and low has NO relation to high/low pitch, it’s simply the articulation position in the mouth)
So why are they called yin and yang?
Ans: When pronouncing the yang vowels, do you find that they sound brighter, clearer and sharper compared to the yin vowels which sounds lower, deeper. Hence the reference to ying and yang.
Vowel alternations are used mostly in onomatopoeics to differentiate between the ‘degree’ of expressions.
소복하다: to be in neat stacks
수북하다: to be in piles
Besides vowel alternations, Korean does have consonant alternations, albeit to a small extent. So how do consonants alternate?
Ans: They alternate between lax, reinforced and aspirated consonants. (예: ㅂ ㅃ ㅍ)
The best examples on how vowel and consonant alternations work together is in describing color intensity.
Red – deep to light (left to right)
Bright: 새빨갛다 – 빨갛다 – 발갛다 – 붉다 – 발그스름하다
Dark: 시뻘겋다 – 뻘겋다 – 벌겋다 – 붉다 – 벌그스름하다
Prefixes,suffixes and vowel/consonant alternations are all employed to show the gradual change from deep to light and bright to dark.