"소년은 어린이입니다."

a가 안 붙을 수는 없는 건가요?

is a는 왜붙나요?

I put "boy is a child" and it's "A boy is a child" I should have gotten it right >:I

is a붙는 이유알고싶어요!

The boy is a child는 틀린건가요..꼭 a boy해야하남ㅠ

"A boy is a child." is an unnatural sentence. "The boy is a child" is ok, and if it's a general statement it would be "boys are children", but I can't imagine a situation in which people would use "A boy is a child."