“ㄴ Addition” – A Lesser Known Sound Change Rule (ㄴ 첨가) | Korean FAQ
Learning every sound change rule in Korean can take a long time, and is usually not necessary in the beginning stages. Simply being exposed to enough Korean, combined with the knowledge of the basic sound change rules, is often enough to get going.
This is a sound change rule that even many Korean speakers are not aware that they're making, and it has to do with the sound 이 and the letter ㄴ. It's known as ㄴ첨가 and is an important sound change rule to learn - especially if you've encountered words that use this rule but weren't aware why it happens.