serious is part of the Basic English 850.
- A problem or situation is serious if it is not funny or comical, but important.
- This is a serious problem. We must do something.
- A person is serious if the person is not laughing or joking, but saying what they mean.
- I see. When you said the room was empty, you were serious!
- The woman's face looked serious, so I knew she was saying something important.