It could be judged as "stealing" and "cheating".
In Korea, when people write their articles, they usually copy other's work easily. They even don't know it is plagiarism. So it is necessary to let them know that is an illegal act.
Then how to prevent plagiarism?
There are several ways to prevent it: using quotation, citation, and paraphrasing.
It looks easy to use quotation and citation. However paraphrasing is little difficult. When we paraphrase other's work, we need to understand the writer's intention and know more beyond background with the article.
I understand how to prevent plagiarism at least. I will try to use quotation when I use other's work and moreover I will more try paraphrase from original articles.