Simple Vowels

Hangul has eight simple vowels.

Traditionally ㅐ andㅔ are not considered in this category. They are the combination of ㅏ + ㅣ = ㅐ and ㅓ + ㅣ = ㅔ. However, in modern Korean they represent simple vowels.
The pronunciation of these vowels are very similar. Many native Korean speakers do not differentiate between the two.

In the dictionary, around 40% of the words are spelled with ㅔ and 60% with ㅐ, out of those that contain these letters.