Verb + 는 중이다 : be in the middle of doing something
. Another way of expressing the progressive tense in Korean.
. Often shortened to: Verb + 는 중
. Also found in the form: Noun + 중
이 식료품은 판매 중입니다 - (The sale of this foodstuff is in process) - This foodstuff is (being) for sale.
Any velar (k, g, ng) before a nasal (m, n) is pronounced "ng." Any labial (p, b, m) before a nasal is pronounced "m." Any dental (t, d, s, n) before a nasal is pronounced "n." An "l" after anything but a vowel or another "l" is pronounced "n" so in this word we end up with a velar before a nasal, "gl" > "ngn."