a.

1. 严重的；危急的；令人担心的
   His error is serious.

   他的错误很严重。

2. 严肃的，庄严的
   He was kind and affectionate, but very serious.

   他仁慈、亲切，但非常严肃。

3. 认真的；不是开玩笑的；当真的[（+about/in）]
   I was pretty serious in what I said at dinner.

   我晚餐时说的话是当真的。

4. 重要的；须认真对待的
   Getting married is a serious matter.

   结婚是件大事。

5. （文学，音乐等）严肃的，非供消遣（或娱乐）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。

6. 宗教的；伦理学的
7. 热衷的，极感兴趣的[（+about）]
   He is not serious about literature.

   他对文学不感兴趣。

adj.

1. demanding or characterized by careful consideration or application.
   ▸solemn or thoughtful.
2. sincere and in earnest, rather than joking or half-hearted.
3. significant or worrying in terms of danger or risk:
   serious injury.
4. informal substantial in terms of size, number, or quality:
   serious money.