确信的英文：
firmly believe
be convinced
be sure
be confident

参考例句：

I feel quite sure about getting the scholarship.
我很确信能得到奖学金。

The police are anxious to apprehend a middle-aged man believed to be armed with a gun.
警察急于逮捕一名确信携有枪支的中年人。

They were sanguine that they would win.
他们确信自己会赢(参看1b)。

They were sanguine about [of] victory.
他们对胜利表示乐观[确信会胜利](参看1c)。

My bike seems to touch a sensitive chord in people, and I'm not quite sure what or why that is.
我的自行车似乎触动了人们一根敏感的心弦，但我不能确信那是什么，又为什么会那样。

Be certain of;be sure of
确信..

Feel sure of;feel certain of
确信..

Be sure of; be certain of
确信;确保

It is my sincere belief that...
我确信...

To inform positively;assure.
使确信斩钉截铁地告知；使确信

firmly是什么意思：
adv. 坚固地；稳固地；坚定地；坚决地

Grasp the thistle firmly
毅然处理困难局面

The struts are firmly braced.
那些支柱上得很牢固。

The tables are firmly fixed to the floor.
这些桌子被牢牢地固定在地上。

believe是什么意思：
v. 相信，认为

Believe not all you hear, tell not all you believe.
言不可尽信，信不可尽言。

I believe they will be on at that time.
我相信他们到时候会同意的。

He does not believe in portion.
他不相信命运。

convinced是什么意思：
adj. 坚信的，确信的，深信的；坚定不移的

It's convincible.
这是可使人信服的。

Can you convince my father?
你能说服我爸爸吗?

Convince your dad? Nothing to it!
说服你爸爸?那太容易了!