certain的副词形式为certainly。certain可作形容词和代词，作为形容词时，中文含义有确实、确定、肯定、无疑、某事、某人等，作为代词时，中文含义为某些；certainly作为certain的副词形式，中文含义有无疑、肯定、当然。
一、certain的中文意思及用法介绍
1、可作形容词，意为确实;确定;肯定;确信;无疑;(不提及细节时用)某事，某人，某种。
例句：She looks certain to win an Oscar.
看来奥斯卡金像奖非她莫属。
If you want to be certain of getting a ticket, book now.
要想有把握买到票，现在就得预订。
Are you absolutely certain about this?
你对这事绝对确信无疑吗？
For certain personal reasons I shall not be able to attend.
由于某种个人原因，我将不能出席。
It was a certain Dr Davis who performed the operation.
是一位叫戴维斯的医生做的手术。
2、还可作代词，意为(不提及人或事物的名称时用)某些。
例句：Certain of those present were unwilling to discuss the matter further.
某些在场的人不愿意进一步讨论这个问题。
二、certainly的中文意思及双语例句
certainly作为副词，意为无疑;确定;肯定;当然;行。
例句：Without treatment, she will almost certainly die.
要是不治疗，她十有八九会死。
Beating the world champions is certainly a big ask for the team.
这个队要打败世界冠军当然难度很大。
The visit to the Far East certainly broadened our horizons.
这次远东之行确实开阔了我们的眼界。
I can certainly feel the effects of too many late nights.
我当然能感受到熬夜太多产生的影响。
