sure、certain、definite与positive这些形容词均含“无疑的、确信的”之意。
sure : 侧重主观上对某事确信无疑。
- Shaun isn't sure whether/if he'll be able to come to the party or not.
肖恩不太确定他能否参加这次聚会。
certain与sure同义，但语气比sure强，着重指有确切理由或不容置疑的证据所支持的确信。
- He was quite certain about/of his attacker's identity.
他对袭击他的人的身份很肯定。
definite : 指已毫无怀疑的余地。
- We need a definite answer by tomorrow.
我们需要在明天之前得到明确的答复。
positive : 语气强烈，指对自己的看法或作的结论的正确性有不可动摇的信念。
- "Are you sure it's okay for me to use your mother's car?" "Positive."
“你肯定我可以开你母亲的车？”“完全肯定。”
