He's quite a serious person.

他是一个相当严肃的人。

《柯林斯英汉双解大词典》

Being a serious person has its benefits.

变成一个循规蹈矩的人有其好处。

youdao

Mrs. Clinton is a serious person; this is a serious job.

希拉里夫人是一个严肃的人；这是一项严肃的工作。

youdao

Usually, a person is clowning around if he is being funny when he should be serious.

VOA: special.2009.01.11

But she was very serious, very motivated, very hard working type of person and really a kind of good Catholic girl her entire life.

VOA: special.2010.03.08

This study also found that serious head injuries also increased a person's risk.

VOA: special.2009.04.07

Republicans and Democrats in Ohio all say that he is a serious person who looks out for consumers.

WHITEHOUSE: President Obama��s News Conference on the American Jobs Act

Not until the last fitful months of the Bush Administration did a serious person with a meaningful understanding of communications strategy come to the fore, and even then, it was too late for him to do anything.

CENTERFORSECURITYPOLICY: Center for Security Policy | Getting Serious About Strategic Influence: How to move beyond the State Department��s legacy of failure | Page: 2

Why do they often become not just widely accepted but absolute orthodoxy, the things you have to believe in order to be a Very Serious Person?

FORBES: Raising the Medicare Retirement Age and the Affordable Care Act