relaxed，relaxing 放松的
1、同义词：dangerous，grave，grievous，life-threatening，severe，goodsober，unplayful。
2、反义词：frivolous，playful
例句：
The mistake is not very serious. 这错误不太严重。
Getting married is a serious matter.结婚是件大事。
He is a serious boy.他是个严肃的孩子。
I was pretty serious in what I said at dinner.我晚餐时说的话是当真的。
The play was amusingly written， but its subject was a serious one. 剧本写得风趣逗笑，但其主题则是严肃的。
