The ㄴ-Insertion Environment
ㄴ insertion is a common pronunciation pattern in some compound or derived words. When the first element ends in a consonant and the next element begins with 이, 야, 여, 요, or 유, a ㄴ sound may appear at the boundary.
This pattern depends on the word's structure and lexical convention. It does not apply automatically to every word containing these vowel spellings.
What to inspect
See whether the first element ends in a consonant.
Check whether the next element begins with an 이-series vowel.
Confirm that the particular compound or derived word uses ㄴ insertion.
Learn the standard spelling and the expected sound together. The spelling does not change.
Verified Spelling Versus Sound
Read each standard spelling before listening. Bracketed forms are pronunciation guides, not replacement spellings.
Spelling · Sound · Why
꽃잎 · [꼰닙] · ㄴ appears before 잎 and the final consonant becomes nasal before ㄴ.
깻잎 · [깬닙] · ㄴ appears before 잎 and the final consonant becomes nasal before ㄴ.
솜이불 · [솜니불] · ㄴ appears before 이불.
맨입 · [맨닙] · ㄴ appears before 입.
색연필 · [생년필] · ㄴ appears before 연필 and final ㄱ becomes nasal before ㄴ.
한여름 · [한녀름] · ㄴ appears before 여름.
The written forms stay 꽃잎 깻잎 솜이불 맨입 색연필 and 한여름.
When Two Changes Meet
An inserted ㄴ can create a second local change. After ㄴ appears, a preceding final consonant may become a nasal sound before ㄴ.
Stage and result
Spelling · Stage 1 after ㄴ insertion · Final sound
꽃잎 · 꽃닙 · [꼰닙]
깻잎 · 깻닙 · [깬닙]
색연필 · 색년필 · [생년필]
Chain order: first hear the added ㄴ, then notice nasalization before ㄴ where it applies. 솜이불 [솜니불], 맨입 [맨닙], and 한여름 [한녀름] mainly let you hear the inserted ㄴ without the same extra change.