‘ㅎ’ 불규칙

When an adjective stem ending in ㅎ is added to an ending that begins with a vowel, ㅎ is omitted.

1. When endings beginning in vowels other than -아/어 are added to adjective stems ending in ㅎ, ㅎ is omitted.

2. When endings beginning in -아/어 are added to adjective stems ending in ㅎ, ㅎ is omitted, and ㅣ is added.

Although the stems of 좋다 (to be good), 많다 (many), 낳다 (to bear, to give birth to), and 넣다 (to put in, to insert) etc. end in ㅎ they are conjugated regularly.

When the stems of 이렇다, 그렇다, 저렇다 and 어떻다 are added to endings that begin with -아/어, they conjugate to 이래, 그래, 저래 and 어때 instead of 이레, 그레, 저레 and 어떼.

• On verb and when the ending start with a 으, both ㅎ and 으 are omitted.
  

• On verb and when the ending start with a 아 or 어, ㅎ is omitted and ㅣ is added.
  

• Otherwise, on verb and when the ending start with a vowel, ㅎ is omitted.

• List of verb not affected by the ㅎ irregular rule, these are conjugated normally: 넣다, 낳다, 좋다, 많다, 찧다, 쌓다, 싫다 and 괜찮다.