“轻心”常常和“掉以”一起用，说成“掉以轻心”，意思是对事情不够小心。

"轻心" is often used together with "掉以" as "掉以轻心", meaning to be careless about something.

单独用“轻心”不常见，你更容易在成语里看到它。

"轻心" is rarely used alone; you are more likely to see it in idioms.