careful的比較級是more careful，最高級是the most careful。careful的意思是小心；注意；謹慎；細緻的；精心的；慎重的。careful用作表語時，其後也可跟動詞不定式、that從句。careful和about連用是“小心”的意思，通常後接指物的名詞、動名詞或從句。
例句：
Careful on those stairs。走那幾段樓梯要當心。
You have to be careful what you say on telly。在電視上説話時你必須很謹慎。
I asked her to be more careful in future。我要她以後更加小心。
Can't you be a bit more careful with my bike？你騎我的車就不能更小心點嗎？
Such an occasion demands the most careful consideration。這樣的場合需要最周到的考慮。
We all think he is one of the most careful students in his class。我們都認為他是班裏最細心的學生之一。
